Previous Article | Next Article ![]()
J. Bacteriol., 10 1997, 6112-6121, Vol 179, No. 19
TA Henderson, KD Young, SA Denome and PK Elf
Two proteins that bind penicillin were observed in Escherichia coli
infected with lambda phages 141, 142, 650, and 651 from the Kohara genomic
library. These phages carry chromosomal DNA fragments that do not contain
any known penicillin binding protein (PBP) genes, indicating that
unrecognized gene products were exhibiting penicillin binding activity. The
genes encoding these proteins were subcloned, sequenced, and identified.
One gene was ampC, which encodes a chromosomal class C beta-lactamase. The
second gene was located at about 8.5 min on the E. coli genomic map and is
a previously uncharacterized open reading frame, here named ampH, that
encodes a protein closely related to the class C beta-lactamases. The
predicted AmpH protein is similar in length to AmpC, but there are
extensive alterations in the amino acid sequence between the SXXK and YXN
motifs of the two proteins. AmpH bound strongly to penicillin G, cefoxitin,
and cephalosporin C; was temperature sensitive; and disappeared from cells
after overnight incubation in stationary phase. Although closely related to
AmpC and other class C beta-lactamases, AmpH showed no beta- lactamase
activity toward the substrate nitrocefin. Mutation of the ampC and/or ampH
genes in E. coli lacking PBPs 1a and 5 produced morphologically aberrant
cells, particularly in cell filaments induced by aztreonam. Thus, these two
members of the beta-lactamase family exhibit characteristics similar to
those of the classical PBPs, and their absence affects cell morphology.
These traits suggest that AmpC and AmpH may play roles in the normal course
of peptidoglycan synthesis, remodeling, or recycling.
Copyright © 1997, American Society for Microbiology
AmpC and AmpH, proteins related to the class C beta-lactamases, bind penicillin and contribute to the normal morphology of Escherichia coli
Department of Microbiology and Immunology, School of Medicine, University of North Dakota, Grand Forks 58202-9037, USA.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»