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J. Bacteriol., 06 1997, 3625-3631, Vol 179, No. 11
L Ramadurai and RK Jayaswal
A gene encoding an autolytic activity was identified in an autolysis-
deficient mutant (Lyt-) of Staphylococcus aureus which produces only a
single band in autolytic-activity gels (N. Mani, P. Tobin, and R. K.
Jayaswal, J. Bacteriol. 175:1493-1499, 1993). An open reading frame,
designated lytM, of 948 bp that could encode a polypeptide of 316 amino
acid residues was identified. The calculated molecular mass of the lytM
gene product (34.4 kDa) corresponded to that of the autolytic activity
detected (approximately 36 kDa) in the Lyt- mutant. Results deduced from
amino acid sequence analysis and N-terminal amino acid sequencing data
suggest that LytM is a secreted protein. The C-terminal region of the
putative protein encoded by lytM showed 51% identity with the N- terminal
region of the mature lysostaphin from Staphylococcus simulans and 50%
identity with the N-terminal region of ALE-1 from Staphylococcus capitis
EPK1. Northern blot analysis showed that lytM expresses a transcript of
approximately 955 bp, as predicted from the DNA sequence. Escherichia coli
clones carrying the lytM gene exhibited autolytic-activity bands of
approximately 36 kDa as well as of 19 and 22 kDa in activity gels. The lytM
gene was mapped to the SmaI-D fragment on the S. aureus chromosome. Mapping
data and results of hybridization experiments with primers generated from
gene sequences of known autolytic genes of S. aureus clearly indicate that
the lytM gene is distinct from other staphylococcal autolytic genes
reported to date.
Copyright © 1997, American Society for Microbiology
Molecular cloning, sequencing, and expression of lytM, a unique autolytic gene of Staphylococcus aureus
Department of Biological Sciences, Illinois State University, Normal 61790-4120, USA.
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