PURIFICATION AND CHARACTERIZATION OF THE FLAGELLAR HOOK-BASAL BODY COMPLEX OF BACILLUS SUBTILIS

摘要

The flagellar hook-basal body (HBB) complex of the Gram-positive bacterium Bacillus subtilis was purified and analysed by electron microscopy, gel electrophoresis, and amino acid sequencing of the major component proteins. The purified HBB complex consisted of the inner (M and S) rings, a rod and a hook. There were no outer (P and L) rings that are found in Gram-negative bacteria. The hook was 15 nm in thickness and 70 nm in length, which is thinner and longer than the hook of Salmonella typhimurium. The hook protein had an apparent molecular mass of 29 kDa, and its N-terminal sequence was identical to that of B. subtilis FlgG, which was previously reported as a rod protein. The sequence of the reported FlgG protein of B. subtilis is more closely related to that of FlgE (the hook protein) rather than FlgG (the rod protein) of S. typhimurium, in spite of the difference of the apparent molecular masses between the two hook proteins (29 kDa versus 42 kDa). The hook-basal body contained six major proteins (with apparent molecular masses of 82, 59, 35, 32, 29 and 20-kDa) and two minor proteins (23 kDa and 13 kDa), which consistently appeared from preparation to preparation. The N-terminus of each of these proteins was sequenced. Comparison with protein databases revealed the following polypeptide-gene correspondences: 82 kDa, fliF; 59 kDa, flgK; 35 kDa, orfF; 32 kDa, yqhF; 23 kDa, orf3 of the flaA locus; 20 kDa, flgB and flgC; 13 kDa, not determined. The band at 20 kDa was a mixture of FlgB and FlgC, as revealed by two-dimensional gel analysis. Characteristic features of B. subtilis HBB are discussed in comparison with those of S. typhimiurium. [References: 36]