SEQUENCE AND EXPRESSION ANALYSIS OF THE HRPB PATHOGENICITY OPERON OF XANTHOMONAS-CAMPESTRIS PV VESICATORIA WHICH ENCODES 8 PROTEINS WITH SIMILARITY TO COMPONENTS OF THE HRP, YSC, SPA, AND FLI SECRETION SYSTEMS
S. Fenselau et U. Bonas, SEQUENCE AND EXPRESSION ANALYSIS OF THE HRPB PATHOGENICITY OPERON OF XANTHOMONAS-CAMPESTRIS PV VESICATORIA WHICH ENCODES 8 PROTEINS WITH SIMILARITY TO COMPONENTS OF THE HRP, YSC, SPA, AND FLI SECRETION SYSTEMS, Molecular plant-microbe interactions, 8(6), 1995, pp. 845-854
In this paper we describe the molecular characterization of hrpB, the
largest operon in the Xanthomonas campestris pv. vesicatoria hrp clust
er. The hrpB region encompasses 6 kb and encodes eight putative protei
ns, seven of which were expressed in Escherichia coli. The HrpB3 prote
in is the only one carrying a signal peptide sequence at the N-terminu
s and is a putative lipoprotein localized in the outer membrane of X.
campestris pv. vesicatoria. The HrpB4 and HrpB8 proteins contain one a
nd five putative transmembrane domains, respectively, and are most lik
ely associated with the inner membrane. The HrpB3, HrpB5, HrpB6, and H
rpB8 proteins show sequence similarity to putative components of diffe
rent type III protein secretion pathways in bacteria. Examples include
Hrp proteins from other plant pathogens, YscJ, YscN, YscL, and YscT o
f Yersinia spp., and MxiJ, Spa47, and Spa29 of Shigella flexneri. The
transcription start site and the hrpB promoter was identified. The min
imal hrpB promoter region of 90 bp contains a novel sequence motif, th
e PIP-box, which might play a role in transcription activation of the
hrpB operon and possibly other plant-induced genes of X. campestris pv
. vesicatoria.