MOLECULAR AND BIOCHEMICAL-ANALYSIS OF A 105 KDA MYCOPLASMA-GALLISEPTICUM CYTADHESIN (GAPA)

The identification of a gene (gapA) from Mycoplasma gallisepticum with homology to the P1 cytadherence gene of Mycoplasma pneumoniae is repo rted. The gapA gene is a 2895 bp ORF encoding a protein with a molecul ar mass of 105 kDa. Nucleotide sequence analysis of the gapA gene reve aled 45% homology to the M. pneumoniae P1 gene, 46% homology to the My coplasma genitalium MgPa gene and 47% homology to the Mycoplasma pirum P1-like protein gene. It has a 64 mol% A+T content compared to 46, 60 and 72 mol% respectively for the P1, MgPa and the PI-like protein gen es. As with the P1 and MgPa genes, gapA is a central gene in a multi-g ene operon, but unlike the P1 and MgPa genes, there is only a single c opy of gapA in the genome. GapA is a trypsin-sensitive surface-exposed protein. Chicken tracheal-ring inhibition-of-attachment assays, using anti-GapA Fab fragments, resulted in 64% inhibition of attachment. Th ese results indicated that GapA plays a role in cytadherence of M. gal lisepticum to host cells.