scholarly journals The Amelogenin C-Terminus Is Required for Enamel Development

2009 ◽  
Vol 89 (2) ◽  
pp. 165-169 ◽  
Author(s):  
M.K. Pugach ◽  
Y. Li ◽  
C. Suggs ◽  
J.T. Wright ◽  
M.A. Aragon ◽  
...  
Keyword(s):  
Amino Acids ◽  
Transgenic Mice ◽  
Physical Characteristics ◽  
Full Length ◽  
Wild Type ◽  
Severe Phenotype ◽  
Enamel Thickness ◽  
C Terminus ◽  
Microct Analysis

The abundant amelogenin proteins are responsible for generating proper enamel thickness and structure, and most amelogenins include a conserved hydrophilic C-terminus. To evaluate the importance of the C-terminus, we generated transgenic mice that express an amelogenin lacking the C-terminal 13 amino acids (CTRNC). MicroCT analysis of TgCTRNC29 teeth (low transgene number) indicated that molar enamel density was similar to that of wild-type mice, but TgCTRNC18 molar enamel (high transgene number) was deficient, indicating that extra transgene copies were associated with a more severe phenotype. When amelogenin-null (KO) and TgCTRNC transgenic mice were mated, density and volume of molar enamel from TgCTRNCKO offspring were not different from those of KO mice, indicating that neither TgCTRNC18 nor TgCTRNC29 rescued enamel’s physical characteristics. Because transgenic full-length amelogenin partially rescues both density and volume of KO molar enamel, it was concluded that the amelogenin C-terminus is essential for proper enamel density, volume, and organization.

scholarly journals The sustainability of interactions between the orexin-1 receptor and β-arrestin-2 is defined by a single C-terminal cluster of hydroxy amino acids and modulates the kinetics of ERK MAPK regulation

2005 ◽  
Vol 387 (3) ◽  
pp. 573-584 ◽  
Author(s):  
Sandra MILASTA ◽  
Nicholas A. EVANS ◽  
Laura ORMISTON ◽  
Shelagh WILSON ◽  
Robert J. LEFKOWITZ ◽  
...  
Keyword(s):  
Amino Acids ◽  
Fluorescent Protein ◽  
Weak Interactions ◽  
Dependent Manner ◽  
Wild Type ◽  
Erk Mapk ◽  
Hydroxy Amino ◽  
C Terminus ◽  
Green Fluorescent ◽  
Kinetics Of

The orexin-1 receptor interacts with β-arrestin-2 in an agonist-dependent manner. In HEK-293T cells, these two proteins became co-internalized into acidic endosomes. Truncations from the C-terminal tail did not prevent agonist-induced internalization of the orexin-1 receptor or alter the pathway of internalization, although such mutants failed to interact with β-arrestin-2 in a sustained manner or produce its co-internalization. Mutation of a cluster of three threonine and one serine residue at the extreme C-terminus of the receptor greatly reduced interaction and abolished co-internalization of β-arrestin-2–GFP (green fluorescent protein). Despite the weak interactions of this C-terminally mutated form of the receptor with β-arrestin-2, studies in wild-type and β-arrestin-deficient mouse embryo fibroblasts confirmed that agonist-induced internalization of this mutant required expression of a β-arrestin. Although without effect on agonist-mediated elevation of intracellular Ca2+ levels, the C-terminally mutated form of the orexin-1 receptor was unable to sustain phosphorylation of the MAPKs (mitogen-activated protein kinases) ERK1 and ERK2 (extracellular-signal-regulated kinases 1 and 2) to the same extent as the wild-type receptor. These studies indicate that a single cluster of hydroxy amino acids within the C-terminal seven amino acids of the orexin-1 receptor determine the sustainability of interaction with β-arrestin-2, and indicate an important role of β-arrestin scaffolding in defining the kinetics of orexin-1 receptor-mediated ERK MAPK activation.

scholarly journals Analysis of the structural features of the C-terminus of GLUT1 that are required for transport catalytic activity

1995 ◽  
Vol 311 (2) ◽  
pp. 699-704 ◽  
Author(s):  
A Muraoka ◽  
M Hashiramoto ◽  
A E Clark ◽  
L C Edwards ◽  
H Sakura ◽  
...  
Keyword(s):  
Amino Acids ◽  
Glucose Transport ◽  
Cytochalasin B ◽  
Point Mutations ◽  
Chinese Hamster ◽  
Structural Features ◽  
Transport Activity ◽  
Wild Type ◽  
C Terminus ◽  
Wild Type Clone

C-terminally truncated and mutated forms of GLUT1 have been constructed to determine the minimum structure at the C-terminus required for glucose transport activity and ligand binding at the outer and inner binding sites. Four truncated mutants have been constructed (CTD24 to CTD27) in which 24 to 27 amino acids are deleted. In addition, point substitutions of R468-->L, F467-->L and G466-->E have been produced. Chinese hamster ovary clones which were transfected with these mutant GLUT1s were shown, by Western blotting and cell-surface carbohydrate labelling, to have expression levels which were comparable with the wild-type clone. Wild-type levels of 2-deoxy-D-glucose transport activity were retained only in the clone transfected with the construct in which 24 amino acids were deleted (CTD24). The CTD25, CTD26 and CTD27 clones showed markedly reduced transport activity. From a kinetic comparison of the CTD24 and CTD26 clones it was found that the reduced transport was mainly associated with a reduced Vmax. value for 2-deoxy-D-glucose uptake but with a slight lowering of the Km. These data establish that the 24 amino acids at the C-terminus of GLUT1 are not required for the transport catalysis. However, the point mutations of F467L and G466E (26 and 27 residues from the C-terminus) did not significantly perturb the kinetics of 2-deoxy-D-glucose transport. The substitution of R468L produced a slight, but significant, lowering of the Km. The ability of the truncated GLUt1s to bind the exofacial ligand, 2-N-4-(1-zai-2,2,2-trifluoroethyl)benzoyl-1,3-bis-(D-mannos- 4-yl-oxy) -2-propylamine (ATB-BMPA), and the endofacial ligand, cytochalasin B, were assessed by photolabelling procedures. The ability to bind ATB-BMPA was retained only in the CTD24 truncated mutant and was reduced to levels comparable with those of the non-transfected clone in the other mutant clones. Cytochalasin B labelling was unimpaired in all four mutated GLUT1s. These data establish that a minimum structure at the C-terminus of GLUT1, which is required for the conformational change to expose the exofacial site, includes amino acids at positions Phe-467 and Arg-468; however, these amino acids are not individually essential.

scholarly journals Localization of Functional Domains of the Mitogenic Toxin of Pasteurella multocida

2001 ◽  
Vol 69 (12) ◽  
pp. 7839-7850 ◽  
Author(s):  
Gillian D. Pullinger ◽  
R. Sowdhamini ◽  
Alistair J. Lax
Keyword(s):  
Amino Acids ◽  
Fusion Proteins ◽  
Pasteurella Multocida ◽  
Transmembrane Domain ◽  
Polyclonal Antibodies ◽  
Full Length ◽  
Cell Binding ◽  
Terminal Fragment ◽  
C Terminus ◽  
N Terminus

ABSTRACT The locations of the catalytic and receptor-binding domains of thePasteurella multocida toxin (PMT) were investigated. N- and C-terminal fragments of PMT were cloned and expressed as fusion proteins with affinity tags. Purified fusion proteins were assessed in suitable assays for catalytic activity and cell-binding ability. A C-terminal fragment (amino acids 681 to 1285) was catalytically active. When microinjected into quiescent Swiss 3T3 cells, it induced changes in cell morphology typical of toxin-treated cells and stimulated DNA synthesis. An N-terminal fragment with a His tag at the C terminus (amino acids 1 to 506) competed with full-length toxin for binding to surface receptors and therefore contains the cell-binding domain. The inactive mutant containing a mutation near the C terminus (C1165S) also bound to cells in this assay. Polyclonal antibodies raised to the N-terminal PMT region bound efficiently to full-length native toxin, suggesting that the N terminus is surface located. Antibodies to the C terminus of PMT were microinjected into cells and inhibited the activity of toxin added subsequently to the medium, confirming that the C terminus contains the active site. Analysis of the PMT sequence predicted a putative transmembrane domain with predicted hydrophobic and amphipathic helices near the N terminus over the region of homology to the cytotoxic necrotizing factors. The C-terminal end of PMT was predicted to be a mixed α/β domain, a structure commonly found in catalytic domains. Homology to proteins of known structure and threading calculations supported these assignments.

p53 domains: structure, oligomerization, and transformation

1994 ◽  
Vol 14 (8) ◽  
pp. 5182-5191
Author(s):  
P Wang ◽  
M Reed ◽  
Y Wang ◽  
G Mayr ◽  
J E Stenger ◽  
...  
Keyword(s):  
Amino Acids ◽  
Dna Binding ◽  
Gel Filtration ◽  
Dominant Negative ◽  
Wild Type ◽  
C Terminus ◽  
Tetramerization Domain ◽  
Wild Type P53 ◽  
Negative Phenotype

Wild-type p53 forms tetramers and multiples of tetramers. Friedman et al. (P. N. Friedman, X. B. Chen, J. Bargonetti, and C. Prives, Proc. Natl. Acad. Sci. USA 90:3319-3323, 1993) have reported that human p53 behaves as a larger molecule during gel filtration than it does during sucrose gradient sedimentation. These differences argue that wild-type p53 has a nonglobular shape. To identify structural and oligomerization domains in p53, we have investigated the physical properties of purified segments of p53. The central, specific DNA-binding domain within murine amino acids 80 to 320 and human amino acids 83 to 323 behaves predominantly as monomers during analysis by sedimentation, gel filtration, and gel electrophoresis. This consistent behavior argues that the central region of p53 is globular in shape. Under appropriate conditions, however, this segment can form transient oligomers without apparent preference for a single oligomeric structure. This region does not enhance transformation by other oncogenes. The biological implications of transient oligomerization by this central segment, therefore, remain to be demonstrated. Like wild-type p53, the C terminus, consisting of murine amino acids 280 to 390 and human amino acids 283 to 393, behaves anomalously during gel filtration and apparently has a nonglobular shape. Within this region, murine amino acids 315 to 350 and human amino acids 323 to 355 are sufficient for assembly of stable tetramers. The finding that murine amino acids 315 to 360 enhance transformation by other oncogenes strongly supports the role of p53 tetramerization in oncogenesis. Amino acids 330 to 390 of murine p53 and amino acids 340 to 393 of human p53, which have been implicated by Sturzbecher et al. in tetramerization (H.-W. Sturzbecher, R. Brain, C. Addison, K. Rudge, M. Remm, M. Grimaldi, E. Keenan, and J. R. Jenkins, Oncogene 7:1513-1523, 1992), do not form stable tetramers under our conditions. Our findings indicate that p53 has at least two autonomous oligomerization domains: a strong tetramerization domain in its C-terminal region and a weaker oligomerization domain in the central DNA binding region of p53. Together, these domains account for the formation of tetramers and multiples of tetramers by wild-type p53. The tetramerization domain is the major determinant of the dominant negative phenotype leading to transformation by mutant p53s.

ADAMTS13 Expressed In Platelets Offers Systemic Protection Against Arterial Thrombosis and Therapeutic Benefits In Murine Models Of Thrombotic Thrombocytopenic Purpura

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 446-446
Author(s):  
Brandy Pickens ◽  
Yingying Mao ◽  
X. Long Zheng
Keyword(s):  
Platelet Count ◽  
Transgenic Mice ◽  
Thrombotic Thrombocytopenic Purpura ◽  
Arterial Thrombosis ◽  
Oxidative Injury ◽  
Therapeutic Benefit ◽  
Full Length ◽  
Murine Models ◽  
Wild Type ◽  
Thrombocytopenic Purpura

ADAMTS13, a plasma metalloprotease, cleaves von Willebrand factor (VWF) and inhibits arterial thrombosis and inflammatory response. Deficiency of plasma ADAMTS13, due hereditary mutations in ADAMTS13 gene or autoantibodies against ADAMTS13 protease, results in a potentially fatal syndrome, thrombotic thrombocytopenic purpura (TTP). Plasma infusion or exchange is the only effective therapy available to date. To develop novel therapeutics against TTP, we tested a hypothesis that recombinant ADAMTS13, expressed specifically in platelets, may offer systemic protection against arterial thrombosis and therefore provide therapeutic benefit for TTP. To test this hypothesis, we first generated transgenic mice (JAX B6SJL) carrying a human full-length ADAMTS13 gene under a murine platelet glycoprotein 1b (CD41) promoter. The transgenic mice were then bred with Adamts13-/- (CAST/Ei) mice for >4 generations. By Western blotting and activity assay, we show that a full-length human ADAMTS13 protein (∼195 kDa) and its proteolytic activity toward a FRETS-hVWF73 peptide are detected in platelet lysate obtained from transgenic (rA13-PltTG) mice but not in Adamts13-/- mice or wild-type mice. Little to no ADAMTS13 activity was detected in plasma in transgenic mice, suggesting the expressed human ADAMTS13 is stored inside platelets. ADAMTS13 was releasable upon stimulation with thrombin (1 U/ml), collagen (10 µg/ml), and AYPGKF (0.5 mM). More significantly, rA13-PltTG mice had higher baseline platelet count than Adamts13-/- mice, but exhibited a dramatically reduced rate of thrombus formation in mesenteric arterioles after oxidative injury with 10% ferric chloride as compared with Adamts13-/-mice and wild-type mice. Finally, rA13-PltTG mice were protected from Shigatoxin-2 (Stx-2) or murine recombinant VWF (mVWF)-induced “TTP-like” syndrome, as demonstrated by fewer rA13-PltTG mice having thrombocytopenia (defined by a 40% drop in platelet count from the baseline after challenge with Stx-2 or mVWF), faster and more complete recovery of thrombocytopenia, and significantly higher survival rate than Adamts13-/- mice. In summary, we have generated transgenic mice expressing human ADAMTS13 in platelets. Platelet ADAMTS13 is releasable upon stimulation by agonists and biologically functional in proteolytic cleavage of VWF in vitro. The platelet-derived ADAMTS13 offers systemic protection against arterial thrombosis after oxidative injury and provide a therapeutic benefit to murine models of TTP, resulting from hereditary ADAMTS13 deficiency. We are now in the process testing the efficacy of this strategy as a novel therapeutic for acquired TTP with inhibitors. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Chemotaxis of Escherichia coli to Pyrimidines: a New Role for the Signal Transducer Tap

2007 ◽  
Vol 190 (3) ◽  
pp. 972-979 ◽  
Author(s):  
Xianxian Liu ◽  
Rebecca E. Parales
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Growth Conditions ◽  
Wild Type ◽  
E Coli ◽  
C Terminus ◽  
Signaling Domain ◽  
Chemotaxis Proteins ◽  
Periplasmic Domain

ABSTRACT Escherichia coli exhibits chemotactic responses to sugars, amino acids, and dipeptides, and the responses are mediated by methyl-accepting chemotaxis proteins (MCPs). Using capillary assays, we demonstrated that Escherichia coli RP437 is attracted to the pyrimidines thymine and uracil and the response was constitutively expressed under all tested growth conditions. All MCP mutants lacking the MCP Tap protein showed no response to pyrimidines, suggesting that Tap, which is known to mediate dipeptide chemotaxis, is required for pyrimidine chemotaxis. In order to confirm the role of Tap in pyrimidine chemotaxis, we constructed chimeric chemoreceptors (Tapsr and Tsrap), in which the periplasmic and cytoplasmic domains of Tap and Tsr were switched. When Tapsr and Tsrap were individually expressed in an E. coli strain lacking all four native MCPs, Tapsr mediated chemotaxis toward pyrimidines and dipeptides, but Tsrap did not complement the chemotaxis defect. The addition of the C-terminal 19 amino acids from Tsr to the C terminus of Tsrap resulted in a functional chemoreceptor that mediated chemotaxis to serine but not pyrimidines or dipeptides. These results indicate that the periplasmic domain of Tap is responsible for detecting pyrimidines and the Tsr signaling domain confers on Tapsr the ability to mediate efficient chemotaxis. A mutant lacking dipeptide binding protein (DBP) was wild type for pyrimidine taxis, indicating that DBP, which is the primary chemoreceptor for dipeptides, is not responsible for detecting pyrimidines. It is not yet known whether Tap detects pyrimidines directly or via an additional chemoreceptor protein.

scholarly journals Ornithine decarboxylase stability in HMOA and DH23b cells is not due to post-translational truncation of a C-terminal recognition site

1996 ◽  
Vol 318 (3) ◽  
pp. 879-882
Author(s):  
John L. A. MITCHELL ◽  
Chung-youl CHOE ◽  
Gary G JUDD
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ornithine Decarboxylase ◽  
Cdna Sequence ◽  
Carboxypeptidase Y ◽  
Amino Acid Residues ◽  
Wild Type ◽  
C Terminus ◽  
Variant Cell ◽  
Sds Page

The normally labile ornithine decarboxylase (ODC) becomes unusually stable when Cys-441 is replaced with Trp in the variant cell lines HMOA and DH23b. This stable ODC is also observed to have higher mobility on SDS/PAGE. Because previous studies have shown that ODC stability can be achieved when as few as five amino acid residues are removed from its C-terminus, it was suggested that the amino acid substitution in the variant ODC might alter its conformation sufficiently to promote a similar proteolytic loss of a C-terminal degradation signal, resulting in a stable yet active ODC. To examine this mechanism, amino acids in the C-terminal regions of both wild-type and stable (Trp-441) ODC proteins were released, by means of carboxypeptidase-Y digestion, and identified by HPLC. The C-terminal ends were found to be the same, and are as predicted from the cDNA sequence. This study proves that stability of the Trp-441 form of ODC is not simply due to proteolytic removal of a C-terminal proteasome-targeting sequence, thereby implying that the stabilization of this mutant ODC form must result directly from a conformational change associated with the loss of Cys-441.

Kinetic Analysis of the Interactions Between the Different ELL and EAF Proteins Involved in Acute Myeloid Leukemia

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3116-3116
Author(s):  
Nimisha Sharma ◽  
Elena Solomaha ◽  
Federico Simone ◽  
Michael Thirman
Keyword(s):  
Amino Acids ◽  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Full Length ◽  
Fusion Partner ◽  
Transcriptional Elongation ◽  
C Terminus ◽  
N Terminus ◽  
Acute Myeloid

Abstract The ELL gene was first cloned as a fusion partner of MLL in the (11;19)(q23;p13.1) translocation that occurs in acute myeloid leukemia. Subsequently, the ELL2 gene was cloned on the basis of its sequence homology to ELL. Both proteins stimulate the rate of transcript elongation by RNA polymerase II. Previously, we isolated two closely related proteins, EAF1 and EAF2, which interact with ELL and ELL2. Deletion mapping studies carried out to delineate the domain(s) of ELL involved in its interaction with either EAF1 or EAF2 showed that the N-terminus (amino acids 1–207) of ELL binds to both EAF1 and EAF2. In comparison, the middle region (207–411 amino acids) does not bind to either of the two EAF proteins and the C-terminus region (411–621 amino acids) binds only to the EAF1 protein. Biochemical studies have revealed that EAF1 and EAF2 enhance the rate of mRNA chain elongation by the ELL proteins in vitro. Although both ELL and ELL2 have similar roles in transcriptional elongation, ELL2 has not been shown to be involved in any hematological abnormality so far. In an attempt to gain a deeper understanding of the biology and functions of the interactions between these different proteins, we determined the kinetic properties of these interactions using the biophysical techniques of surface plasmon resonance (SPR) and isothermal calorimetry (ITC). SPR detects complex formation in real time and provides a better comprehension of the dynamics of association and dissociation of an interaction, and ITC is used to determine the thermodynamics of the interaction. Our SPR analysis has provided novel insights into the nature of the binding of the ELL proteins to the EAF proteins. We observed that both ELL and ELL2 bind to EAF1 and EAF2 with a high affinity, but the binding affinity of ELL2 for both EAF1 and EAF2 is almost twelve-fold greater than the affinity of ELL for both the EAF proteins. The higher affinity of ELL2 is due to much slower uptake and release kinetics reflected by the low association and dissociation rate constants of ELL2 compared to ELL. The stoichiometry of ELL, ELL2, EAF1 and EAF2 in the ELL-EAF1, ELL-EAF2, ELL2-EAF1 and ELL2-EAF2 complexes was estimated to be 1:1 after fitting the respective sensorgrams obtained by SPR analysis to the Langmuir’s bimolecular model. Interestingly, we did not observe any difference in the affinity of either ELL or ELL2 for binding to EAF1 or EAF2. We used SPR-based competition experiments to show that ELL and ELL2 bind to the same sites on the EAF proteins. We have also investigated the characteristics of binding of the various ELL domains to the EAF1/2 proteins. In the (11;19)(q23;p13.1) translocation, the C-terminus of ELL fuses to the N-terminus of MLL to generate a chimeric protein that interacts with EAF1 and this interaction is critical for the role of ELL in cell immortalization in vitro and leukemogenesis in vivo. In agreement with this observation, we found that the C-terminus of ELL binds EAF1 with a higher affinity than EAF2, while the N-terminus of ELL binds with similar affinities and displays similar kinetics of binding to both EAF1 and EAF2. We also found that the individual binding sites on the ELL N-terminus and the C-terminus exhibited a lower affinity for the EAF proteins, but the affinity increases when the two sites function together in the context of the full-length protein, suggesting that the two sites co-operate with each other to increase the affinity for the full-length ELL protein. Taken together, these observations suggest that although ELL and ELL2 share many similarities in terms of their sequence and function in transcription elongation, they bind to the EAF proteins with different affinities and kinetics. Alternative interaction dynamics and the interplay between the different ELL and EAF proteins permit distinct functional regulation of transcriptional elongation in normal and leukemic cells.

scholarly journals Tethered Sir3p nucleates silencing at telomeres and internal loci in Saccharomyces cerevisiae.

1996 ◽  
Vol 16 (5) ◽  
pp. 2483-2495 ◽  
Author(s):  
A J Lustig ◽  
C Liu ◽  
C Zhang ◽  
J P Hanish
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Binding Sites ◽  
Associated Factors ◽  
Wild Type ◽  
Gain Of Function ◽  
Telomeric Silencing ◽  
C Terminus ◽  
Lexa Binding ◽  
In Cis

Rap1p binds to sites embedded within the Saccharomyces cerevisiae telomeric TG1-3 tract. Previous studies have led to the hypothesis that Rap1p may recruit Sir3p and Sir3p-associating factors to the telomere. To test this, we tethered Sir3p adjacent to the telomere via LexA binding sites in the rap1-17 mutant that truncates the Rap1p C-terminal 165 amino acids thought to contain sites for Sir3p association. Tethering of LexA-Sir3p adjacent to the telomere is sufficient to restore telomeric silencing, indicating that Sir3p can nucleate silencing at the telomere. Tethering of LexA-Sir3p or the LexA-Sir3p(N2O5) gain-of-function protein to a telomeric LexA site hyperrepresses an adjacent ADE2 gene in wild-type cells. Hence, Sir3p recruitment to the telomere is limiting in telomeric silencing. In addition, LexA-Sir3p(N2O5) hyperrepresses telomeric silencing when tethered to a subtelomeric site 3.6 kb from the telomeric tract. This hyperrepression is dependent on the C terminus of Rap1p, suggesting that subtelomeric LexA-Sir3p(N205) can interact with Rap1p-associated factors at the telomere. We also demonstrate that LexA-Sir3p or LexA-Sir3p(N205) tethered in cis with a short tract of telomeric TG1-3 sequences is sufficient to confer silencing at an internal chromosomal position. Internal silencing is enhanced in rap1-17 strains. We propose that sequestration of silencing factors at the telomere limits the efficiency of internal silencing.

scholarly journals C-terminus of mitotic centromere-associated kinesin (MCAK) inhibits its lattice-stimulated ATPase activity

2004 ◽  
Vol 383 (2) ◽  
pp. 227-235 ◽  
Author(s):  
Ayana MOORE ◽  
Linda WORDEMAN
Keyword(s):  
Amino Acids ◽  
Atpase Activity ◽  
Energy Cost ◽  
Atp Hydrolysis ◽  
Molecular Motor ◽  
Full Length ◽  
Apparent Affinity ◽  
Tubulin Dimer ◽  
C Terminus

Mitotic centromere-associated kinesin (MCAK) is a microtubule (MT)-destabilizing molecular motor. In the present study we show that the final 8 amino acids of the C-terminus of MCAK inhibit lattice-stimulated ATPase activity of the motor. Surprisingly, loss of this C-terminal ‘tail’ (MCAK-Q710) leads to more rapid depolymerization of MTs relative to full-length MCAK (wt-MCAK). Biochemical and microscopic assays revealed that MCAK-Q710 bound to the MT lattice with higher apparent affinity as compared with wt-MCAK. End-stimulated depolymerization was similar for both enzymes. These data suggest that lattice-bound MCAK can increase the rate of MT depolymerization, but at an energy cost. The function of the C-terminus of MCAK may be to selectively inhibit lattice-stimulated ATPase activity, resulting in limited interactions of the motor with the MT lattice. This increases the coupling between ATP hydrolysis and tubulin dimer release, but it also limits MT depolymerization.

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