3toi
Tailoring Enzyme Stability and Exploiting Stability-Trait Linkage by Iterative Truncation and Optimization
Structural highlights
FunctionBLAT_ECOLX TEM-type are the most prevalent beta-lactamases in enterobacteria; they hydrolyze the beta-lactam bond in susceptible beta-lactam antibiotics, thus conferring resistance to penicillins and cephalosporins. TEM-3 and TEM-4 are capable of hydrolyzing cefotaxime and ceftazidime. TEM-5 is capable of hydrolyzing ceftazidime. TEM-6 is capable of hydrolyzing ceftazidime and aztreonam. TEM-8/CAZ-2, TEM-16/CAZ-7 and TEM-24/CAZ-6 are markedly active against ceftazidime. IRT-4 shows resistance to beta-lactamase inhibitors. Publication Abstract from PubMedThe stability of proteins is paramount for their therapeutic and industrial use, and thus, is a major task for protein engineering. Several types of chemical and physical stabilities are desired and discussion revolves around whether each stability trait needs to be addressed separately and how specific and compatible stabilizing mutations act. We demonstrate a step-wise perturbation-compensation strategy, which identifies mutations rescuing activity of a truncated TEM beta-lactamase. Analyses relating structural stress with the external stresses of heat, denaturants, and proteases, reveal our second-site suppressors as general stability centers that also improve the full-length enzyme. A library of lactamase variants truncated by 15 N-terminal and 3 C-terminal residues (Bla-NDelta15CDelta3) was subjected to activity selection and DNA shuffling. The resulting clone with the best in vivo performance harbored eight mutations, surpassed the full-length wild-type protein by 5.3 degrees C in Tm, displayed significantly higher catalytic activity at elevated temperatures, and showed delayed guanidine-induced denaturation. The crystal structure of this mutant was solved and provided insights into its stability determinants. Stepwise reconstitution of the N- and C-terminus increased its thermal, denaturant and proteolytic resistance successively, leading to a full-length enzyme with a Tm increased by 15.3 degrees C and a half-denaturation concentration shifted from 0.53 to 1.75 M guanidinium relative to that of the wild type. These improvements demonstrate that iterative truncation-optimization cycles can exploit stability-trait linkages in proteins and are exceptionally suited for the creation of progressively stabilized variants and/or down-sized proteins without the need for detailed structural or mechanistic information. Exploring Molecular Linkage of Protein Stability Traits for Enzyme Optimization by Iterative Truncation and Evolution.,Speck J, Hecky J, Tam HK, Arndt KM, Einsle O, Muller KM Biochemistry. 2012 Apr 30. PMID:22545913[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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