SEQUENCING AND ANALYSIS OF THE DIVERGON COMPRISING GTAB, THE STRUCTURAL GENE OF UDP-GLUCOSE PYROPHOSPHORYLASE OF BACILLUS-SUBTILIS-168

Nucleotide sequencing revealed that gtaB, the structural gene of UDP-g lucose pyrophosphorylase (EC 2.7.7.9), is part of a divergon-like gene tic entity. The latter consists of two monocistronic operons gtaB and orfX, transcribed from a 245 bp regulatory region, each encoding an ac idic protein with a molecular mass of 33.0 and 42.6 kDa, respectively. gtaB is transcribed from a distal P-A promoter, and a proximal P-B pr omoter which is negatively controlled by the Sin protein. Six-mediated transcriptional attenuation and enhancement of P-B and P-D, respectiv ely, suggest that these promoters control functions which antagonize e ach other. Transcription of orfX is mediated by a P-A promoter. The re gulatory region comprises four ATGAAA hexamers, present as two inverse repeats. Protein GtaB exhibits high homology to analogous prokaryotic enzymes, while OrfX shows 55.4% homology with the product of Escheric hia coli o389, which is part of a regulatory unit involved in sugar pr ocessing. Mutations gtaB515 and gtaB(g)100, which define different bac teriophage adsorption patterns, were sequenced. They are transitions l eading to substitution of amino acids which occupy conserved positions , and are thus likely to be part of an enzyme active site. The nature of the possible receptors for defective bacteriophages PBSY and PBSZ i s discussed.