Evolution of antibiotic resistance: several different amino acid substitutions in an active site loop alter the substrate profile of ?-lactamase

1994 ◽  
Vol 12 (2) ◽  
pp. 217-229 ◽  
Author(s):  
Timothy Palzkill ◽  
Quyen-Quyen Le ◽  
K. V. Venkatachalam ◽  
Mark LaRocco ◽  
Hermes Ocera
Keyword(s):  
Antibiotic Resistance ◽  
Amino Acid ◽  
Active Site ◽  
Amino Acid Substitutions

scholarly journals Investigation of the Role of Electrostatic Charge in Activation of the Escherichia coli Response Regulator CheY

2003 ◽  
Vol 185 (21) ◽  
pp. 6385-6391 ◽  
Author(s):  
Jenny G. Smith ◽  
Jamie A. Latiolais ◽  
Gerald P. Guanga ◽  
Sindhura Citineni ◽  
Ruth E. Silversmith ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Signal Transduction ◽  
Amino Acid ◽  
Active Site ◽  
Response Regulator ◽  
Residual Activity ◽  
Phosphoryl Group ◽  
Sensor Kinase ◽  
Amino Acid Substitutions ◽  
Flagellar Rotation

ABSTRACT In a two-component regulatory system, an important means of signal transduction in microorganisms, a sensor kinase phosphorylates a response regulator protein on an aspartyl residue, resulting in activation. The active site of the response regulator is highly charged (containing a lysine, the phosphorylatable aspartate, two additional aspartates involved in metal binding, and an Mg2+ ion), and introduction of the dianionic phosphoryl group results in the repositioning of charged moieties. Furthermore, substitution of one of the Mg2+-coordinating aspartates with lysine or arginine in the Escherichia coli chemotaxis response regulator CheY results in phosphorylation-independent activation. In order to examine the consequences of altered charge distribution for response regulator activity and to identify possible additional amino acid substitutions that result in phosphorylation-independent activation, we made 61 CheY mutants in which residues close to the site of phosphorylation (Asp57) were replaced by various charged amino acids. Most substitutions (47 of 61) resulted in the complete loss of CheY activity, as measured by the inability to support clockwise flagellar rotation. However, 10 substitutions, all introducing a new positive charge, resulted in the loss of chemotaxis but in the retention of some clockwise flagellar rotation. Of the mutants in this set, only the previously identified CheY13DK and CheY13DR mutants displayed clockwise activity in the absence of the CheA sensor kinase. The absence of negatively charged substitution mutants with residual activity suggests that the introduction of additional negative charges into the active site is particularly deleterious for CheY function. Finally, the spatial distribution of positions at which amino acid substitutions are functionally tolerated or not tolerated is consistent with the presently accepted mechanism of response regulator activation and further suggests a possible role for Met17 in signal transduction by CheY.

scholarly journals Biochemical properties of recombinant acetylcholinesterases with amino acid substitutions in the active site

2007 ◽  
Vol 42 (3) ◽  
pp. 367-373 ◽  
Author(s):  
Suenghyup Oh ◽  
Toshinori Kozaki ◽  
Takashi Tomita ◽  
Yoshiaki Kono
Keyword(s):  
Amino Acid ◽  
Active Site ◽  
Biochemical Properties ◽  
Amino Acid Substitutions

scholarly journals Proposed Signal Transduction Role for Conserved CheY Residue Thr87, a Member of the Response Regulator Active-Site Quintet

1998 ◽  
Vol 180 (14) ◽  
pp. 3563-3569 ◽  
Author(s):  
Jeryl L. Appleby ◽  
Robert B. Bourret
Keyword(s):  
Amino Acid ◽  
Active Site ◽  
Response Regulator ◽  
Hydroxyl Group ◽  
Amino Acid Substitutions ◽  
Mutant Proteins ◽  
Hydroxy Amino Acid ◽  
Hydroxy Amino ◽  
Flagellar Rotation

ABSTRACT CheY serves as a structural prototype for the response regulator proteins of two-component regulatory systems. Functional roles have previously been defined for four of the five highly conserved residues that form the response regulator active site, the exception being the hydroxy amino acid which corresponds to Thr87 in CheY. To investigate the contribution of Thr87 to signaling, we characterized, genetically and biochemically, several cheY mutants with amino acid substitutions at this position. The hydroxyl group appears to be necessary for effective chemotaxis, as a Thr→Ser substitution was the only one of six tested which retained a Che+ swarm phenotype. Although nonchemotactic, cheY mutants with amino acid substitutions T87A and T87C could generate clockwise flagellar rotation either in the absence of CheZ, a protein that stimulates dephosphorylation of CheY, or when paired with a second site-activating mutation, Asp13→Lys, demonstrating that a hydroxy amino acid at position 87 is not essential for activation of the flagellar switch. All purified mutant proteins examined phosphorylated efficiently from the CheA kinase in vitro but were impaired in autodephosphorylation. Thus, the mutant CheY proteins are phosphorylated to a greater degree than wild-type CheY yet support less clockwise flagellar rotation. The data imply that Thr87 is important for generating and/or stabilizing the phosphorylation-induced conformational change in CheY. Furthermore, the various position 87 substitutions differentially affected several properties of the mutant proteins. The chemotaxis and autodephosphorylation defects were tightly linked, suggesting common structural elements, whereas the effects on self-catalyzed and CheZ-mediated dephosphorylation of CheY were uncorrelated, suggesting different structural requirements for the two dephosphorylation reactions.

scholarly journals Capsular Type and Antibiotic Resistance in Streptococcus agalactiae Isolates from Patients, Ranging from Newborns to the Elderly, with Invasive Infections

2009 ◽  
Vol 53 (6) ◽  
pp. 2650-2653 ◽  
Author(s):  
Somay Yamagata Murayama ◽  
Chizuko Seki ◽  
Hiroshi Sakata ◽  
Katsuhiko Sunaoshi ◽  
Eiichi Nakayama ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Amino Acid ◽  
Streptococcus Agalactiae ◽  
Gel Electrophoresis ◽  
The Elderly ◽  
Pulsed Field Gel Electrophoresis ◽  
Amino Acid Substitutions ◽  
Capsular Type ◽  
Invasive Infections ◽  
Resistant Strains

ABSTRACT Streptococcus agalactiae isolates (n = 189) from patients with invasive infections were analyzed for capsular type by PCR, for antimicrobial susceptibility, and for the presence of resistance genes. In contrast to the predominance of capsular type III in children, types Ib and V were most common among adults. All 45 levofloxacin-resistant strains had two amino acid substitutions, Ser81Leu in the gyrA gene and Ser79Phe in the parC gene, and showed similar pulsed-field gel electrophoresis patterns.

scholarly journals Prediction of the Evolution of Ceftazidime Resistance in Extended-Spectrum β-Lactamase CTX-M-9

2006 ◽  
Vol 50 (2) ◽  
pp. 731-738 ◽  
Author(s):  
J. Delmas ◽  
F. Robin ◽  
F. Carvalho ◽  
C. Mongaret ◽  
R. Bonnet
Keyword(s):  
Catalytic Activity ◽  
Amino Acid ◽  
Active Site ◽  
Random Mutagenesis ◽  
Evolutionary Process ◽  
Catalytic Efficiency ◽  
Kinetic Constants ◽  
The Other ◽  
Amino Acid Substitutions ◽  
Evolutionary Potential

ABSTRACT A random mutagenesis technique was used to predict the evolutionary potential of β-lactamase CTX-M-9 toward the acquisition of improved catalytic activity against ceftazidime. Thirty CTX-M mutants were obtained during three rounds of mutagenesis. These mutants conferred 1- to 128-fold-higher MICs of ceftazidime than the parental enzyme CTX-M-9. The CTX-M mutants contained one to six amino acid substitutions. Mutants harbored the substitutions Asp240Gly and Pro167Ser, which were previously observed in clinical CTX-M enzymes. Additional substitutions, notably Arg164His, Asp179Gly, and Arg276Ser, were observed near the active site. The kinetic constants of the three most active mutants revealed two distinct ways of improving catalytic efficiency against ceftazidime. One enzyme had a 17-fold-higher k cat value than CTX-M-9 against ceftazidime. The other two had 75- to 300-fold-lower Km values than CTX-M-9 against ceftazidime. The current emergence of CTX-M β-lactamases with improved activity against ceftazidime may therefore be the beginning of an evolutionary process which might subsequently generate a great diversity of CTX-M-type ceftazidimases.

scholarly journals Multiple substitutions lead to increased loop flexibility and expanded specificity in Acinetobacter baumannii carbapenemase OXA-239

2018 ◽  
Vol 475 (1) ◽  
pp. 273-288 ◽  
Author(s):  
Thomas M. Harper ◽  
Cynthia M. June ◽  
Magdalena A. Taracila ◽  
Robert A. Bonomo ◽  
Rachel A. Powers ◽  
...  
Keyword(s):  
Amino Acid ◽  
Acinetobacter Baumannii ◽  
Active Site ◽  
Active Sites ◽  
Protein Structures ◽  
Amino Acid Substitutions ◽  
The Third ◽  
Class D ◽  
Late Generation ◽  
Loop Flexibility

OXA-239 is a class D carbapenemase isolated from an Acinetobacter baumannii strain found in Mexico. This enzyme is a variant of OXA-23 with three amino acid substitutions in or near the active site. These substitutions cause OXA-239 to hydrolyze late-generation cephalosporins and the monobactam aztreonam with greater efficiency than OXA-23. OXA-239 activity against the carbapenems doripenem and imipenem is reduced ∼3-fold and 20-fold, respectively. Further analysis demonstrated that two of the substitutions (P225S and D222N) are largely responsible for the observed alteration of kinetic parameters, while the third (S109L) may serve to stabilize the protein. Structures of OXA-239 with cefotaxime, doripenem and imipenem bound as acyl-intermediates were determined. These structures reveal that OXA-239 has increased flexibility in a loop that contains P225S and D222N. When carbapenems are bound, the conformation of this loop is essentially identical with that observed previously for OXA-23, with a narrow active site that makes extensive contacts to the ligand. When cefotaxime is bound, the loop can adopt a different conformation that widens the active site to allow binding of that bulky drug. This alternate conformation is made possible by P225S and further stabilized by D222N. Taken together, these results suggest that the three substitutions were selected to expand the substrate specificity profile of OXA-23 to cephalosporins and monobactams. The loss of activity against imipenem, however, suggests that there may be limits to the plasticity of class D enzymes with regard to evolving active sites that can effectively bind multiple classes of β-lactam drugs.

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