Difference in Structure of the Gene Encoding H~+-ATPase between Streptococcus bovis and Ruminococcus albus

摘要

The full sequences of the genes encoding H+-ATPase of Streptococcus bovis and Ruminococcus albus were determined by the inverse PCR. The atp operon of S. bovis was approximately 6.5 kbp and consisted of atp E (c-subunit), B (a), F (b), H (δ), A (α),G (γ), D (β), and C (ε) in this order. The subunit order of atp E and B was reversed in S. bovis, when compared to the arrangement in R. albus and many other bacteria. In R. albus, two open reading frames (ORF), which potentially encode 13.7 and 14.9kDa proteins, were found in the area upstream of atp B. This area corresponds to the region of atp I (inhibitor protein) in Escherichia coli. There was no ORF that potentially encodes atp I in S. bovis. The δ-subunit signature found in many bacteria was not present in S. bovis, whereas the δ-subunit signature was not found in R. albus. The absence of the δ-subunit signature may partly explain that the H~+-ATPase of R. albus is less stable and active than that of S. bovis, since this motif sequence is considered to be important for catalytic activity and the assembly of subunits. There were many differences between S. bovis and R. albus in deduced amino acid sequences of both structural and regulatory regions, but it is difficult to explain at present how the differences affect the function of H~+-ATPase, or the regulation of the synthesis of the enzyme.