Sequence analysis and characterization of the hmw gene cluster of Mycoplasma pneumoniae.

Mycoplasma pneumoniae (Mp) cytadherence requires the proper anchoring of cytadhesin proteins in the mycoplasmal membrane at an attachment organelle through their interaction with a cytoskeleton-like network of accessory proteins that includes HMW1 and HMW3. Approximately 8.25 kb of Mp DNA was sequenced, beginning at the 3' end of the hmw3 gene and continuing through hmw1. Comparison of the resulting deduced amino acid (aa) sequence with N terminus and internal peptide aa sequences from purified HMW1 permitted definitive identification of hmw1. HMW1 was characterized with respect to structure, hydrophobicity, possible phosphoacceptor sites and expression of the Mp recombinant protein in Escherichia coli. In addition, HMW1 membrane topography was examined for antibody accessibility on the mycoplasmal surface. hmw3 and hmw1 flank four open reading frames (ORFs) spanning approximately 4.3 kb and in the same orientation as the hmw genes. The sequences of their deduced products were evaluated for likely structural features and comparison with protein data banks. Finally, the Mp rpsD analog was identified immediately downstream from hmw1.