Characterization of a hemin-storage locus ofYersinia pestis

Abstract

The pigmentation phenotype (Pgm⁺) ofYersinia pestis refers to temperature-dependent storage of hemin as well as expression of a number of other physiological characteristics. Spontaneous mutation to a Pgm⁻ phenotype occurs via a large chromosomal deletion event and results in the inability to express the Pgm⁺ characteristics. In this study, we have used transposon insertion mutants to define two regions of a hemin-storage (hms) locus. A clone (pHMSI) encompassing this locus reinstates expression of hemin storage (Hms⁺) inY. pestis spontaneous Pgm⁻ strains KIM and Kuma but not inEscherichia coli. Complementation analysis using subclones of pHMS1 inY. pestis transposon mutants indicates that both regions (hmsA andhmsB), which are separated by about 4 kb of intervening DNA, are essential for expression of the Hms⁺ phenotype. The 9.1-kb insert of pHMS1 contains structural genes encoding 90-kDa, 72-kDa, and 37-kDa polypeptides. Two-dimensional gel electrophoresis analysis of cells from Pgm⁺, spontaneous Pgm⁻, and Hms⁻ transposon strains, as well as a spontaneous Pgm⁻ strain transformed with pHMS1, indicated that two families of surface-exposed polypeptides (of about 87 and 69-73 kDa) are associated with the Hms⁺ phenotype.