IDENTIFICATION AND SEQUENCE-ANALYSIS OF THE SOXB GENE ESSENTIAL FOR SULFUR OXIDATION OF PARACOCCUS-DENITRIFICANS GB17

The coding region for lithotrophic sulfur oxidation (Sox) in Paracoccu s denitrificans GB17 was identified by isolation of a transposon Tn5-m ob mutant with a Sox(-) phenotype (strain TP19). The corresponding wil d-type region was cloned previously (G. Mittenhuber, K. Sonomoto, M. E gert, and C. G. Friedrich, J. Bacteriol. 173:7340-7344, 1991). Sequenc e analysis of a 2.5-kb subclone that complemented strain TP19 revealed that Tn5-mob was inserted into a coding region for a 553-amino-acid p olypeptide named SoxB. This polypeptide had an M(r) of 60.573, includi ng a possible signal peptide. The function of the SoxB protein of P. d enitrificans GB17 appeared to be identical to that of enzyme B of the thiosulfate-oxidizing enzyme system of Thiobacillus versutus. The amin o acid compositions of the two proteins mere identical, and the amino acid sequences of three internal peptides of enzyme B as determined by Edman degradation were identical to corresponding sequences of the de duced SoxB protein of P. denitrificans GB17.