The Hydrophobic TraM Protein of pKM101 Is Required for Conjugal Transfer and Sensitivity to Donor-Specific Bacteriophage

pKM101 is a self-transmissible plasmid of the IncN incompatibility group. Analysis of the DNA sequences of the genes required for conjugal transfer suggested the existence of a previously uncharacterized open reading frame, designatedtraM,that might be required for conjugation. Merodiploid strains containing transposon insertion mutations either intraMor in neighboringtragenes were used to demonstrate thattraMconstitutes a new complementation group essential for conjugation and donor phage sensitivity. The hydrophobicity profile of TraM suggests that it contains a signal sequence. The remainder of TraM is also composed predominantly of hydrophobic amino acids but contains one possible surface exposed loop. TraM–alkaline phosphatase and TraM–β-galactosidase fusion proteins supported the hypothesis that TraM has a small cytoplasmic loop. We were unable to detect heterologous complementation between anytramutation and its homolog from thevirBoperon ofAgrobacterium tumefaciens.