STRUCTURE, ORGANIZATION, AND EXPRESSION OF GENES-CODING FOR ENVELOPE COMPONENTS IN THE ARCHAEON METHANOSARCINA-MAZEI S-6

The antigenic mosaics of archaeal species are complex and lead to the distinction of different immunotypes. We began the dissection of the a ntigenic mosaic of the methanogen Methanosarcina mazei mazei S-6 by ge ne cloning and sequencing. The analysis of the sequence, organization, and in vitro (heterologous) and in vivo expression of two three-gene clusters that encode proteins localized to the cell envelope and that are recognized by antibodies for surface structures is presented in th is report. The amino acid sequences and compositions share characteris tics with S-layer proteins and, most notably, have re peats of conserv ed sequences and secondary structures. Expressed genes produced protei ns with a tendency to oligomerize, and one of these proteins was susce ptible to breakdown at regular intervals. Altogether, the data reveal a modular system (clusters of homologous genes, proteins of similar se quences with conserved repeats) seemingly suitable for assembling an e normous variety of final molecular structures by rearranging and combi ning genes, proteins, and repeats. and thus generate the observed wide spectrum of antigenic diversity.