Table 2.

Properties and homologies of proteins of thehmu locus and upstream genes

ProteinMass (kDa)apIaLocationb(putative function)Homology (% similarity/% identity)c
OrfXd??? (unknown)ShuX (67/57)
OrfY23.27.2IM (unknown)ShuY (64/58)
HmuP′4.54.7CP (unknown)Truncated homolog of HemP (68/64)
HmuR74.2/71.24.8/4.7OMe(TonB-dependent receptor)HemR (88/86), ShuA (75/69), ChuA (75/69), HutA (30/23), PhuR
HmuS39.15.4CPe (possibly involved in iron release from heme)HemS (92/89), ShuS (73/66), PhuS (50/43)
HmuT29.6/26.874./5.9PP (periplasm-binding protein)HemT (91/91), ShuT (73/66), PhuT (41/33), HutB (47/35)
HmuU35.511.6IM (permease)HemU (96/93), ShuU (74/68), PhuU (54/58), HutC (51/41)
HmuV29.66.6IMf (ATP-binding protein)HemV (91/88), ShuV (66/59), PhuV (51/45), HutD (51/42)
  • a Calculated masses and pIs were determined for each protein with the IG suite software package. The values for HmuR and HmuT are for unprocessed/processed proteins. Signal cleavage sites for HmuR and HmuT were predicted between amino acids 28 and 29 and between amino acids 25 and 26, respectively, by using the SignalP program (41).

  • b Predicted protein locations were determined with the PSORT program (40). CP, cytoplasmic; PP, periplasmic.

  • c Percent homologies were determined by using the Gap program of the GCG software package. A Gap comparison between HmuR and PhuR showed no significant homology; however, a Bestfit alignment of these two proteins showed 44% similarity of PhuR with HmuR over a stretch of 185 amino acids. Hem proteins are from Y. enterocolitica (accession no. X68147 and X77867 [59, 60]), Shu proteins are from S. dysenteriae(accession no. U64516 [38, 71]), ChuA is from E. coli (accession no. U67920 [67]), Phu proteins are from P. aeruginosa (accession no. AF055999 [43]), and Hut proteins are from V. cholerae (accession no. AF016580 [20, 42]).

  • d The sequence for the gene encoding the deduced OrfX protein is incomplete and lacks a 5′ start site.

  • e Protein locations of HmuR and HmuS were determined by Western blot analysis of cellular fractions of Y. pestis with HmuR- or HmuS-specific polyclonal antibodies.

  • f HmuV, an ATP-binding protein, is most likely associated with HmuU, the IM permease.