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Abstract
Cytadherence or attachment to host tissue is a crucial event in the pathogenesis of infections by Mycoplasma pneumoniae, a common agent of respiratory disease in humans. A large group of cytadherence-accessory proteins work together to localize the major adhesin P1 to the polar attachment organelle in a functional form. The hmw gene cluster, which contains the genes encoding cytadherence-accessory proteins P30, HMW1, and HMW3 in addition to other possible cytadherence proteins, was found to be transcribed from four different promoters in a series of overlapping transcripts that may impact the regulation of genes in the cluster. In another cluster, the p1 operon, genes MPN140-142 were transcribed as polycistronic message. Recombinant genes of the p1 operon encoding the P1 adhesin and the proteins B and C were delivered and expressed in non-adherent mutants lacking some or all of these proteins. Some but not all translation of the gene encoding B/C (MPN142) was linked to the translation of the gene encoding P1 (MPN141). Furthermore, in the absence of P1, B/C were unstable and little or no protein was detected. This linkage of P1/B/C at transcription, translation, and protein stability sheds light on relationships between P1/B/C on the genetic and biochemical level and supports the view of these three proteins as integral members of a single major adhesin complex.