ISOLATION AND CHARACTERIZATION OF TRANSCRIPTION SIGNAL SEQUENCES FROMSTREPTOCOCCUS-THERMOPHILUS

Streptococcus thermophilus (ST) chromosomal DNA fragments generated by partial Sau3A digestion were cloned into the unique BamHI site upstre am from the promoterless chloramphenicol acetyltransferase (car) gene of the Escherichia coli (EC) promoter-probe vector pKK520-3. Recombina nt plasmids containing ST sequences with transcription-activation acti vity were isolated from chloramphenicol-resistant (Cm-R) EC transforma nts, A promoterless Streptomyces antibioticus melanin biosynthesis ope ron (melC) was inserted immediately downstream from the ST sequence to identify DNA with strong promoter activity, Several ST transcription- activation sequences, termed ST(p)s, were isolated and subcloned, and their nucleic acid sequences determined. The -10 and -35 consensus seq uences were identified in these putative ST promoters. Detailed analys is of STP3306 sequence data revealed two partial open reading frames ( ORFs) with high degrees of homology to prokaryotic GTP-binding protein and DNA repair enzyme, thus providing valuable information for furthe r study on DNA maintenance in this important lactic acid bacterium.