Genes encoding the Mycoplasma arthritidis surface-exposed lipoprotein MAA1
were cloned and sequenced from MAA1-expressing strains 158p10p9 and PG6, fr
om a low-adherence (LA) variant derived from 158p10p9 that expresses a trun
cated version of MAA1 (MAA1 Delta) and from two MAA1-negative strains, 158
and H39, The deduced amino acid sequences of maa1 from 158p10p9 and PG6 pre
dicted, respectively, 86.5- and 86.4-kDa basic, Largely hydrophilic lipopro
teins with 29-amino-acid signal peptides and predicted cleavage sites for s
ignal peptidase II (Ala-Ala-Ala down arrow Cys), The truncation in the LA v
ariant resulted from a G-->T substitution at nucleotide 695, which created
a premature stop codon, This, in turn, generated a predicted 26.6-kDa proli
poprotein (23.6 kDa after processing), consistent with an M-r of similar to
24,000 calculated for MAA1 Delta. Similarly, absence of MAA1 expression in
H39 and 158 resulted from C-->A substitutions at nucleotide 208, generatin
g premature stop codons at that site in both strains.