The use of alanine scanning mutagenesis to determine the role of the N-terminus of the regulatory chain in the heterotropic mechanism of Escherichia coli aspartate transcarbamoylase

1994 ◽  
Vol 7 (5) ◽  
pp. 673-679 ◽  
Author(s):  
Niki J. Dembowski ◽  
Evan R. Kantrowitz
Keyword(s):  
Escherichia Coli ◽  
Aspartate Transcarbamoylase ◽  
Alanine Scanning Mutagenesis ◽  
Alanine Scanning ◽  
N Terminus

scholarly journals Comprehensive Alanine-scanning Mutagenesis of Escherichia coli CsrA Defines Two Subdomains of Critical Functional Importance

2006 ◽  
Vol 281 (42) ◽  
pp. 31832-31842
Author(s):  
Jeffrey Mercante ◽  
Kazushi Suzuki ◽  
Xiaodong Cheng ◽  
Paul Babitzke ◽  
Tony Romeo
Keyword(s):  
Escherichia Coli ◽  
Functional Importance ◽  
Alanine Scanning Mutagenesis ◽  
Alanine Scanning

Expression in Escherichia coli of fragments of the coiled-coil rod domain of rabbit myosin: influence of different regions of the molecule on aggregation and paracrystal formation

1991 ◽  
Vol 99 (4) ◽  
pp. 823-836
Author(s):  
S.J. Atkinson ◽  
M. Stewart
Keyword(s):  
Escherichia Coli ◽  
Ionic Strength ◽  
Coiled Coil ◽  
Periodic Variation ◽  
Heptad Repeat ◽  
C Terminus ◽  
N Terminus ◽  
Low Ionic Strength ◽  
Myosin Rod

We have expressed in Escherichia coli a cDNA clone corresponding broadly to rabbit light meromyosin (LMM) together with a number of modified polypeptides and have used this material to investigate the role of different aspects of molecular structure on the solubility properties of LMM. The expressed material was characterized biochemically and structurally to ensure that it retained the coiled-coil conformation of the native molecule. Full-length recombinant LMM retained the general solubility properties of myosin and, although soluble at high ionic strength, precipitated when the ionic strength was reduced below 0.3 M. Constructs in which the ‘skip’ residues (that disrupt the coiled-coil heptad repeat) were deleted had solubility properties indistinguishable from the wild type, which indicated that the skip residues did not play a major role in determining the molecular interactions involved in assembly. Deletions from the N terminus of LMM did not alter the solubility properties of the expressed material, but deletion of 92 residues from the C terminus caused a large increase in solubility at low ionic strength, indicating that a determinant important for interaction between LMM molecules was located in this region. The failure of deletions from the molecule's N terminus to alter its solubility radically suggested that the periodic variation of charge along the myosin rod may not be as important as proposed for determining the strength of binding between molecules and thus the solubility of myosin.

scholarly journals Recognition of Ferric Catecholates by FepA

2004 ◽  
Vol 186 (11) ◽  
pp. 3578-3589 ◽  
Author(s):  
Rajasekaran Annamalai ◽  
Bo Jin ◽  
Zhenghua Cao ◽  
Salete M. C. Newton ◽  
Phillip E. Klebba
Keyword(s):  
Primary Role ◽  
Alanine Scanning Mutagenesis ◽  
Aromatic Residues ◽  
N Terminus ◽  
Direct Binding ◽  
Ligand Transport ◽  
Initial Binding ◽  
Biphasic Release ◽  
Adsorption Stage

ABSTRACT Escherichia coli FepA transports certain catecholate ferric siderophores, but not others, nor any noncatecholate compounds. Direct binding and competition experiments demonstrated that this selectivity originates during the adsorption stage. The synthetic tricatecholate Fe-TRENCAM bound to FepA with 50- to 100-fold-lower affinity than Fe-enterobactin (FeEnt), despite an identical metal center, and Fe-corynebactin only bound at much higher concentrations. Neither Fe-agrobactin nor ferrichrome bound at all, even at concentrations 106-fold above the Kd . Thus, FepA only adsorbs catecholate iron complexes, and it selects FeEnt among even its close homologs. We used alanine scanning mutagenesis to study the contributions of surface aromatic residues to FeEnt recognition. Although not apparent from crystallography, aromatic residues in L3, L5, L7, L8, and L10 affected FepA's interaction with FeEnt. Among 10 substitutions that eliminated aromatic residues, Kd increased as much as 20-fold (Y481A and Y638A) and Km increased as much as 400-fold (Y478), showing the importance of aromaticity around the pore entrance. Although many mutations equally reduced binding and transport, others caused greater deficiencies in the latter. Y638A and Y478A increased Km 10- and 200-fold more, respectively, than Kd . N-domain loop deletions created the same phenotype: Δ60-67 (in NL1) and Δ98-105 (in NL2) increased Kd 10- to 20-fold but raised Km 500- to 700-fold. W101A (in NL2) had little effect on Kd but increased Km 1,000-fold. These data suggested that the primary role of the N terminus is in ligand uptake. Fluorescence and radioisotopic experiments showed biphasic release of FeEnt from FepA. In spectroscopic determinations, k off1 was 0.03/s and k off2 was 0.003/s. However, FepAY272AF329A did not manifest the rapid dissociation phase, corroborating the role of aromatic residues in the initial binding of FeEnt. Thus, the β-barrel loops contain the principal ligand recognition determinants, and the N-domain loops perform a role in ligand transport.

scholarly journals Effect of directional pulling on mechanical protein degradation by ATP-dependent proteolytic machines

2017 ◽  
Vol 114 (31) ◽  
pp. E6306-E6313 ◽  
Author(s):  
Adrian O. Olivares ◽  
Hema Chandra Kotamarthi ◽  
Benjamin J. Stein ◽  
Robert T. Sauer ◽  
Tania A. Baker
Keyword(s):  
Escherichia Coli ◽  
Protein Degradation ◽  
Single Molecule ◽  
Wild Type ◽  
N Terminus ◽  
Multiple Copies ◽  
Rate Limiting ◽  
Hydrolysis Of ◽  
Translocation Speed

AAA+ proteases and remodeling machines couple hydrolysis of ATP to mechanical unfolding and translocation of proteins following recognition of sequence tags called degrons. Here, we use single-molecule optical trapping to determine the mechanochemistry of two AAA+ proteases, Escherichia coli ClpXP and ClpAP, as they unfold and translocate substrates containing multiple copies of the titinI27 domain during degradation initiated from the N terminus. Previous studies characterized degradation of related substrates with C-terminal degrons. We find that ClpXP and ClpAP unfold the wild-type titinI27 domain and a destabilized variant far more rapidly when pulling from the N terminus, whereas translocation speed is reduced only modestly in the N-to-C direction. These measurements establish the role of directionality in mechanical protein degradation, show that degron placement can change whether unfolding or translocation is rate limiting, and establish that one or a few power strokes are sufficient to unfold some protein domains.

scholarly journals Analysis of Hendra Virus Fusion Protein N-Terminal Transmembrane Residues

Viruses ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2353
Author(s):  
Chelsea T. Barrett ◽  
Hadley E. Neal ◽  
Kearstin Edmonds ◽  
J. Lizbeth Reyes Zamora ◽  
Carole L. Moncman ◽  
...  
Keyword(s):  
Host Cell ◽  
Protein Function ◽  
Hendra Virus ◽  
Proteolytic Processing ◽  
Viral Envelope ◽  
Alanine Scanning Mutagenesis ◽  
Alanine Scanning ◽  
F Protein ◽  
The Family ◽  
N Terminus

Hendra virus (HeV) is a zoonotic enveloped member of the family Paramyoxviridae. To successfully infect a host cell, HeV utilizes two surface glycoproteins: the attachment (G) protein to bind, and the trimeric fusion (F) protein to merge the viral envelope with the membrane of the host cell. The transmembrane (TM) region of HeV F has been shown to have roles in F protein stability and the overall trimeric association of F. Previously, alanine scanning mutagenesis has been performed on the C-terminal end of the protein, revealing the importance of β-branched residues in this region. Additionally, residues S490 and Y498 have been demonstrated to be important for F protein endocytosis, needed for the proteolytic processing of F required for fusion. To complete the analysis of the HeV F TM, we performed alanine scanning mutagenesis to explore the residues in the N-terminus of this region (residues 487–506). In addition to confirming the critical roles for S490 and Y498, we demonstrate that mutations at residues M491 and L492 alter F protein function, suggesting a role for these residues in the fusion process.

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