Multigene Families Encoding the Major Hemagglutinins in Phylogenetically Distinct Mycoplasmas

Abstract

Mycoplasma synoviae has two major membrane antigens, MSPA and MSPB, both of which are phase variable and which may be coordinately involved in adhesion of the organism to erythrocytes. A single gene (vlhA) from M. synoviae was characterized, and polypeptides were expressed from nonoverlapping 5′ and 3′ regions in Escherichia coli. The expression product of the vlhA 5′ region reacted with specific reagents against MSPB, while that of the 3′ region reacted with specific reagents against MSPA. Analysis of the predicted amino acid sequence showed a characteristic signal peptidase II cleavage site, and the presence of the acylation site was confirmed by identification of a lipid-associated membrane protein, similar in molecular mass to MSPB, in [3H]palmitate-labelled membrane proteins. Further sequence analysis of the vlhA gene revealed a high identity with the Mycoplasma gallisepticum pMGA1.7 gene, a member of a large translated family. The vlhA gene was shown to hybridize to multiple restriction fragments of the M. synoviae genome, suggesting that it was also a member of a multigene family. These findings indicate that coordinate phase variation of the two major surface antigens of M. synoviaeWVU may be due to their expression from the same gene and that homologous gene families encode the major hemagglutinins of two phylogenetically distinct mycoplasmas. The presence of homologous multigene families in such phylogenetically distinct species, but not in the genomes of more closely related species, suggests that the families may have been transferred horizontally.

Sequence polymorphisms within the pMGA genes and pMGA antigenic variants in Mycoplasma gallisepticum

“…All pMGA genes with determined sequences (pMGA1.1p MGA1.9) have highly conserved leader peptide sequence and encode proline-rich regions (PRR) at the N-terminus with the cysteine (C 1 ) at the ¢rst position [6,8,10]. Our study was focused on the pMGA1.1 and pMGA1.2 genes because of the importance of their products as adhesins and immunodominant antigens [3,4,12].…”

“…1). Di¡erences in the length of PRR are interesting because such regions are characteristic also for the Nterminal part of Mycoplasma synoviae hemagglutinin which has over 63% sequence identity with pMGA1.7 protein [10] and for cytadhesins of Mycoplasma pneumoniae and Mycoplasma genitalium [2]. It is possible, therefore, that di¡erent lengths of PRR might play a role in the adherence of mycoplasmas.…”

Gene conversion and concerted evolution in bacterial genomes

“…In this organism, MSPB (a lipoprotein) and MSPA (a haemagglutinin) are the main surface antigens; these display a high antigenic diversity [101]. Both antigens are encoded by a single gene ( vlhA1 ), which undergoes post‐translational cleavage and modification to yield MSPB and MSPA [102]. Although both the lipoprotein and the haemagglutinin sectors of the gene experience antigenic variation, combinatorial gene conversion is restricted to the haemagglutinin part.…”

The characterization ofMycoplasma synoviaeEF-Tu protein and proteins involved in hemadherence and their N-terminal amino acid sequences

“…Factors which contribute to the chronic form of the disease are unknown but the immunodominant M. synoviae surface membrane proteins, which undergo phase variation in expression and are associated with hemadherence, may at least in part be involved [2–4]. Indeed, there is increasing evidence that immunodominant surface proteins undergo phase variable expression in many Mycoplasma species and are associated with the evasion of the immune response [5–7]. M. synoviae has two major immunogenic membrane proteins, MSPA and MSPB, both of which are phase variable and coordinately involved in adhesion of the organism to erythrocytes [2].…”

“…M. synoviae has two major immunogenic membrane proteins, MSPA and MSPB, both of which are phase variable and coordinately involved in adhesion of the organism to erythrocytes [2]. Recently the vlhA gene encoding a variably expressed lipoprotein which is a hemagglutinin of M. synoviae (WVU 1853 strain) has been identified [7]. In addition, it has been found that MSPA and MSPB proteins are transcribed from a single gene, vlhA [7].…”