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Klebsiella pneumoniae carbapenemase variant 44 (KPC-44) acquires ceftazidime-avibactam resistance by altering the conformation of active site loops.


ABSTRACT: Klebsiella pneumoniae carbapenemase 2 (KPC-2) is an important source of drug resistance as it can hydrolyze and inactivate virtually all β-lactam antibiotics. KPC-2 is potently inhibited by avibactam via formation of a reversible carbamyl linkage of the inhibitor with the catalytic serine of the enzyme. However, the use of avibactam in combination with ceftazidime (CAZ-AVI) has led to the emergence of CAZ-AVI resistant variants of KPC-2 in clinical settings. One such variant, KPC-44, bears a 15 amino-acid duplication in one of the active site loops (270-loop). Here, we show that the KPC-44 variant exhibits higher catalytic efficiency in hydrolyzing ceftazidime, lower efficiency towards imipenem and meropenem, and a similar efficiency in hydrolyzing ampicillin, when compared to the wild-type KPC-2 enzyme. In addition, the KPC-44 variant enzyme exhibits 12-fold lower avibactam carbamylation efficiency than the KPC-2 enzyme. An X-ray crystal structure of KPC-44 showed that the 15 amino acid duplication results in an extended and partially disordered 270-loop and also changes the conformation of the adjacent 240-loop, which in turn has altered interactions with the active-site omega loop. Furthermore, a structure of KPC-44 with avibactam revealed that formation of the covalent complex results in further disorder in the 270-loop, suggesting that rearrangement of the 270-loop of KPC-44 facilitates avibactam carbamylation. These results suggest that the duplication of 15 amino acids in the KPC-44 enzyme leads to resistance to CAZ-AVI by modulating the stability and conformation of the 270-, 240-, and omega-loops.

SUBMITTER: Sun Z 

PROVIDER: S-EPMC10716778 | biostudies-literature | 2023 Nov

REPOSITORIES: biostudies-literature

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Klebsiella pneumoniae carbapenemase variant 44 acquires ceftazidime-avibactam resistance by altering the conformation of active-site loops.

Sun Zhizeng Z   Lin Hanfeng H   Hu Liya L   Neetu Neetu N   Sankaran Banumathi B   Wang Jin J   Prasad B V Venkataram BVV   Palzkill Timothy T  

The Journal of biological chemistry 20231123 1


Klebsiella pneumoniae carbapenemase 2 (KPC-2) is an important source of drug resistance as it can hydrolyze and inactivate virtually all β-lactam antibiotics. KPC-2 is potently inhibited by avibactam via formation of a reversible carbamyl linkage of the inhibitor with the catalytic serine of the enzyme. However, the use of avibactam in combination with ceftazidime (CAZ-AVI) has led to the emergence of CAZ-AVI-resistant variants of KPC-2 in clinical settings. One such variant, KPC-44, bears a 15  ...[more]

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