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J. Bacteriol., Nov 1995, 6033-6040, Vol 177, No. 21
C Binnie, MJ Butler, JS Aphale, R Bourgault, MA DiZonno, P Krygsman, L Liao, E Walczyk and LT Malek
A strain of Streptomyces lividans 66 deleted for a major tripeptidyl
aminopeptidase (Tap) was used as a host to screen an S. lividans genomic
library for clones overexpressing activity against the chromogenic
substrate Ala-Pro-Ala-beta-naphthylamide. In addition to reisolation of the
tap gene, clones representing another locus, slpD, were uncovered. slpD was
analyzed by deletion subcloning to localize its functional sequence.
Nucleotide sequence determination revealed an open reading frame encoding a
55-kDa protein exhibiting significant amino acid sequence homology to Tap,
particularly around the putative active-site serine residue. No secreted
protein was observed for strains harboring the slpD clone, but inspection
of the predicted protein sequence revealed a putative lipoprotein signal
peptide (signal peptidase II type), suggesting a mycelial location for the
SlpD proteinase. In an attempt to isolate an endoprotease known to be
active against some heterologous proteins, a second clone was isolated by
using a longer substrate (t-butyloxycarbonyl [Boc]-APARSPA-beta-
naphthylamide) containing a chemical blocking group at the amino terminus
to prevent aminopeptidase cleavage. This locus, slpE, appeared to also
encode a 55-kDa mycelium-associated (lipoprotein) proteinase, whose
predicted protein sequences showed significant amino acid homology to Tap
and SlpD, particularly around the putative active-site serine residues.
Chromosomal integration and deletion analysis in both the wild-type and
Tap-deficient backgrounds appeared to indicate that SlpD was essential for
viability and SlpE was required for growth on minimal media.
Copyright © 1995, American Society for Microbiology
Isolation and characterization of two genes encoding proteases associated with the mycelium of Streptomyces lividans 66
Cangene Corporation, Mississauga, Canada.
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