scholarly journals Analysis of Ion Interactions with the K+ -dependent Na+/Ca+ Exchangers NCKX2, NCKX3, and NCKX4

2006 ◽  
Vol 282 (7) ◽  
pp. 4453-4462 ◽  
Author(s):  
Frank Visser ◽  
Valeria Valsecchi ◽  
Lucio Annunziato ◽  
Jonathan Lytton
Keyword(s):  
Binding Pocket ◽  
Conformational Flexibility ◽  
Structure And Function ◽  
Hek293 Cells ◽  
Side Chain ◽  
Functional Characteristics ◽  
Structural Context ◽  
Ion Interactions ◽  
And Function ◽  
Low K

K+-dependent Na+/Ca2+ exchangers (NCKX) catalyze cytosolic Ca2+ extrusion and are particularly important for neuronal Ca2+ signaling. Of the five mammalian isoforms, the detailed functional characteristics have only been reported for NCKX1 and -2. In the current study, the functional characteristics of recombinant NCKX3 and -4 expressed in HEK293 cells were determined and compared with those of NCKX2. Although the apparent affinities of the three isoforms for Ca2+ and Na+ were similar, NCKX3 and -4 displayed ∼40-fold higher affinities for K+ ions than NCKX2. Functional analysis of various NCKX2 mutants revealed that mutation of Thr-551 to Ala, the corresponding residue in NCKX4, resulted in an apparent K+ affinity shift to one similar to that of NCKX4 without a parallel shift in apparent Ca2+ affinity. In the converse situation, when Gln-476 of NCKX4 was converted to Lys, the corresponding residue in NCKX2, both the K+ and Ca2+ affinities were reduced. These results indicate that the apparently low K+ affinity of NCKX2 requires a Thr residue at position 551 that may reduce the conformational flexibility and/or K+ liganding strength of side-chain moieties on critical neighboring residues. This interaction appears to be specific to the structural context of the NCKX2 K+ binding pocket, because it was not possible to recreate the K+-specific low affinity phenotype with reciprocal mutations in NCKX4. The results of this study provide important information about the structure and function of NCKX proteins and will be critical to understanding their roles in neuronal Ca2+ signaling.

The structure and function of HPr

1998 ◽  
Vol 76 (2-3) ◽  
pp. 359-367 ◽  
Author(s):  
E Bruce Waygood
Keyword(s):  
Structure And Function ◽  
Side Chain ◽  
Phosphoryl Group ◽  
Phosphotransferase System ◽  
Tertiary Structures ◽  
E Coli ◽  
H Nmr ◽  
Early Protein ◽  
Alpha Beta ◽  
And Function

Histidine-containing phosphocarrier protein, HPr, was one of the early protein tertiary structures determined by two-dimensional 1H-NMR. Tertiary structures for HPrs from Escherichia coli, Bacillus subtilis, and Staphylococcus aureus have been obtained by 1H NMR and the overall folding pattern of HPr is highly conserved, a beta alpha beta beta alpha beta alpha arrangement of three alpha-helices overlaying a four-stranded beta-sheet. High-resolution structures for HPrs from E. coli and B. subtilis have been obtained using 15N- and 13C-labeled proteins. The first application of NMR to the understanding of the structure and function of HPr was to describe the phosphohistidine isomer, Ndelta1-P-histidine in S. aureus phospho-HPr, and the unusual pKas of the His-15 side chain. The pKa values for the His-15 imidazole from more recent studies are 5.4 for HPr and 7.8 for phospho-HPr from E. coli, for example. A consensus description of the active site is proposed for HPr and phospho-HPr. In HPr, His-15 has a defined conformation and N-caps helix A, and is thus affected by the helix dipole. His-15 undergoes a small conformational change upon phosphorylation, a movement to allow the phosphoryl group to be positioned such that it forms hydrogen bonds with the main chain amide nitrogens of residue 16 (not conserved) and Arg-17. Interactions between residue 12 side chain (not conserved: asparagine, serine, and threonine) and His-15, and between the Arg-17 guanidinium group and the phosphoryl group, are either weak or transitory.Key words: HPr, NMR, phosphoenolpyruvate:sugar phosphotransferase system, phosphohistidine, phosphoserine.

scholarly journals Structure and function of the AAA+ nucleotide binding pocket

2012 ◽  
Vol 1823 (1) ◽  
pp. 2-14 ◽  
Author(s):  
Petra Wendler ◽  
Susanne Ciniawsky ◽  
Malte Kock ◽  
Sebastian Kube
Keyword(s):  
Nucleotide Binding ◽  
Binding Pocket ◽  
Structure And Function ◽  
And Function

scholarly journals Evaluating RNA Structural Flexibility: Viruses Lead the Way

Viruses ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 2130
Author(s):  
Connor W. Fairman ◽  
Andrew M. L. Lever ◽  
Julia C. Kenyon
Keyword(s):  
Structural Analysis ◽  
Single Molecule ◽  
Rna Structure ◽  
Conformational Flexibility ◽  
Structure And Function ◽  
Structural Flexibility ◽  
Productive Area ◽  
Biophysical Techniques ◽  
Biological Polymers ◽  
And Function

Our understanding of RNA structure has lagged behind that of proteins and most other biological polymers, largely because of its ability to adopt multiple, and often very different, functional conformations within a single molecule. Flexibility and multifunctionality appear to be its hallmarks. Conventional biochemical and biophysical techniques all have limitations in solving RNA structure and to address this in recent years we have seen the emergence of a wide diversity of techniques applied to RNA structural analysis and an accompanying appreciation of its ubiquity and versatility. Viral RNA is a particularly productive area to study in that this economy of function within a single molecule admirably suits the minimalist lifestyle of viruses. Here, we review the major techniques that are being used to elucidate RNA conformational flexibility and exemplify how the structure and function are, as in all biology, tightly linked.

scholarly journals αIIbβ3 biogenesis is controlled by engagement of αIIb in the calnexin cycle via the N15-linked glycan

Blood ◽  
2006 ◽  
Vol 107 (7) ◽  
pp. 2713-2719 ◽  
Author(s):  
W. Beau Mitchell ◽  
JiHong Li ◽  
Deborah L. French ◽  
Barry S. Coller
Keyword(s):  
Consensus Sequence ◽  
Proteasomal Degradation ◽  
Structure And Function ◽  
Hek293 Cells ◽  
Wild Type ◽  
Mannose Residue ◽  
The Core ◽  
And Function ◽  
Kinetics Of ◽  
Terminal Mannose

AbstractAlthough much is known about αIIbβ3 structure and function, relatively little is understood about its biogenesis. Thus, we studied the kinetics of pro-αIIb production and degradation, focusing on whether proteasomal degradation or the calnexin cycle participates in these processes. In pulse-chase analyses, the time to half-disappearance of pro-αIIb (t1/2) was the same in (1) HEK293 cells transfected with (a) αIIb plus β3, (b) αIIb alone, (c) mutant V298FαIIb plus β3, or (d) I374TαIIb plus β3; and (2) murine wild-type and β3-null megakaryocytes. Inhibition of the proteasome prolonged the t1/2 values in both HEK293 cells and murine megakaryocytes. Calnexin coprecipitated with αIIb from HEK293 cells transfected with αIIb alone, αIIb plus β3, and V298FαIIb plus β3. For proteins in the calnexin cycle, removal of the terminal mannose residue of the middle branch of the core N-linked glycan results in degradation. Inhibition of the enzyme that removes this mannose residue prevented pro-αIIb degradation in β3-null murine megakaryocytes. αIIb contains a conserved glycosylation consensus sequence at N15, and an N15Q mutation prevented pro-αIIb maturation, complex formation, and degradation. Our findings suggest that pro-αIIb engages the calnexin cycle via the N15 glycan and that failure of pro-αIIb to complex normally with β3 results in proteasomal degradation.

scholarly journals Structure and function of an Arabidopsis thaliana sulfate transporter

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lie Wang ◽  
Kehan Chen ◽  
Ming Zhou
Keyword(s):  
Arabidopsis Thaliana ◽  
Plant Growth ◽  
Structure And Function ◽  
Regulatory Function ◽  
Side Chain ◽  
Sulfate Transporter ◽  
Dimer Formation ◽  
Anion Transporters ◽  
Stas Domain ◽  
And Function

AbstractPlant sulfate transporters (SULTR) mediate absorption and distribution of sulfate (SO42−) and are essential for plant growth; however, our understanding of their structures and functions remains inadequate. Here we present the structure of a SULTR from Arabidopsis thaliana, AtSULTR4;1, in complex with SO42− at an overall resolution of 2.8 Å. AtSULTR4;1 forms a homodimer and has a structural fold typical of the SLC26 family of anion transporters. The bound SO42− is coordinated by side-chain hydroxyls and backbone amides, and further stabilized electrostatically by the conserved Arg393 and two helix dipoles. Proton and SO42− are co-transported by AtSULTR4;1 and a proton gradient significantly enhances SO42− transport. Glu347, which is ~7 Å from the bound SO42−, is required for H+-driven transport. The cytosolic STAS domain interacts with transmembrane domains, and deletion of the STAS domain or mutations to the interface compromises dimer formation and reduces SO42− transport, suggesting a regulatory function of the STAS domain.

Structural and mechanistic studies on the peroxisomal oxygenase phytanoyl-CoA 2-hydroxylase (PhyH)

2007 ◽  
Vol 35 (5) ◽  
pp. 870-875 ◽  
Author(s):  
C.J. Schofield ◽  
M.A. McDonough
Keyword(s):  
Binding Sites ◽  
Point Mutations ◽  
Clinical Importance ◽  
Structure And Function ◽  
Side Chain ◽  
Mechanistic Studies ◽  
Pristanic Acid ◽  
Methyl Group ◽  
Refsum's Disease ◽  
And Function

Phytanic acid (PA) is an epimeric metabolite of the isoprenoid side chain of chlorophyll. Owing to the presence of its epimeric β-methyl group, PA cannot be metabolized by β-oxidation. Instead, it is metabolized in peroxisomes via α-oxidation to give pristanic acid, which is then oxidized by β-oxidation. PhyH (phytanoyl-CoA 2-hydroxylase, also known as PAHX), an Fe(II) and 2OG (2-oxoglutarate) oxygenase, catalyses hydroxylation of phytanoyl-CoA. Mutations of PhyH ablate its role in α-oxidation, resulting in PA accumulation and ARD (adult Refsum's disease). The structure and function of PhyH is discussed in terms of its clinical importance and unusual selectivity. Most point mutations of PhyH causing ARD cluster in two distinct groups around the Fe(II)- and 2OG-binding sites. Therapaeutic possibilities for the treatment of Refsum's disease involving PhyH are discussed.

scholarly journals A photochemical C=C cleavage process: toward access to backbone N-formyl peptides

2021 ◽  
Vol 17 ◽  
pp. 2932-2938
Author(s):  
Haopei Wang ◽  
Zachary T Ball
Keyword(s):  
Structure And Function ◽  
Side Chain ◽  
Cleavage Process ◽  
And Function ◽  
Synthetic Approaches ◽  
Formyl Peptides ◽  
Spatiotemporal Control

Photo-responsive modifications and photo-uncaging concepts are useful for spatiotemporal control of peptides structure and function. While side chain photo-responsive modifications are relatively common, access to photo-responsive modifications of backbone N–H bonds is quite limited. This letter describes a new photocleavage pathway, affording N-formyl amides from vinylogous nitroaryl precursors under physiologically relevant conditions via a formal oxidative C=C cleavage. The N-formyl amide products have unique properties and reactivity, but are difficult or impossible to access by traditional synthetic approaches.

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