Molecular characterization of a gene encoding a membrane protein of Spiroplasma citri.

A 9.6-kb genomic DNA segment, previously cloned from the phytopathogen Spiroplasma citri BR3-3X [Fletcher et al. (1981) Phytopathology 71, 1073-1080], contained several open reading frames including one encoding a 58-kDa protein. In this work, the transcription initiation site of the P58 mRNA was mapped and part of the gene was expressed in Escherichia coli as a fusion protein. A synthetic peptide, whose sequence is included in the fusion protein, was produced. Antibodies against both the fusion protein and the peptide reacted with a 60-kDa protein in a S. citri total protein extract. Hydrophobicity characteristics of this protein and its fractionation into the detergent phase indicated that P58, which shares limited sequence similarity with the adhesin of Mycoplasma hominis and the attachment protein of M. genitalium, is an integral membrane protein.