title: Structural basis for the extended substrate spectrum of CMY-10, a plasmid-encoded class C beta-lactamase.
abstract: The emergence and dissemination of extended-spectrum (ES) beta-lactamases induce therapeutic failure and a lack of eradication of clinical isolates even by third-generation beta-lactam antibiotics like ceftazidime. CMY-10 is a plasmid-encoded class C beta-lactamase with a wide spectrum of substrates. Unlike the well-studied class C ES beta-lactamase from Enterobacter cloacae GC1, the Omega-loop does not affect the active site conformation and the catalytic activity of CMY-10. Instead, a three-amino-acid deletion in the R2-loop appears to be responsible for the ES activity of CMY-10. According to the crystal structure solved at 1.55 A resolution, the deletion significantly widens the R2 active site, which accommodates the R2 side-chains of beta-lactam antibiotics. This observation led us to demonstrate the hydrolysing activity of CMY-10 towards imipenem with a long R2 substituent. The forced mutational analyses of P99 beta-lactamase reveal that the introduction of deletion mutations into the R2-loop is able to extend the substrate spectrum of class C non-ES beta-lactamases, which is compatible with the isolation of natural class C ES enzymes harbouring deletion mutations in the R2-loop. Consequently, the opening of the R2 active site by the deletion of some residues in the R2-loop can be considered as an operative molecular strategy of class C beta-lactamases to extend their substrate spectrum.
authors: School of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
authors: Jae Young
authors: JY
authors: Kim
authors: Ha Il
authors: HI
authors: Jung
authors: Young Jun
authors: YJ
authors: An
authors: Jung Hun
authors: JH
authors: Lee
authors: So Jung
authors: SJ
authors: Kim
authors: Seok Hoon
authors: SH
authors: Jeong
authors: Kye Joon
authors: KJ
authors: Lee
authors: Pann-Ghill
authors: PG
authors: Suh
authors: Heung-Soo
authors: HS
authors: Lee
authors: Sang Hee
authors: SH
authors: Lee
authors: Sun-Shin
authors: SS
authors: Cha