The complete covalent structure of protein B. The third major protein degraded during germination of Bacillus megaterium spores.

The complete covalent structure of Protein B, the third major protein degraded during germination of Bacillus megaterium spores, has been determined. The intact protein was cleaved with the specific B. megaterium spore protease into three peptides, residues 1 to 31 (B-III), 32 to 66 (B-I), and 67 to 96 (B-II). Cleavage of the intact protein with trypsin allowed isolation of the peptide encompassing residues 61 to 77 (T-11) as well as the COOH-terminal peptide, residues 94 to 96 (T-4). Cleavage of Peptide B-I with trypsin or chymotrypsin allowed isolation of peptides encompassing residues 53 to 60 (B-I-T-2) and residues 52 to 66 (B-I-C-4), respectively. Subtractive Edman degradation of Peptide T-4, automated sequenator analysis of Peptides B-I, B-II, T-11, B-I-T-2, and B-I-C-4, previously published partial sequence data on the intact B-protein and carboxypeptidase V digestion of the intact protein provided the data from which the following unique sequence was deduced: NH2-Ala-Lys-Gln-Thr-Asn-Lys-Thr-Ala-Ser-Gly-Thr-Ser-Thr-Gln-His-15 Val-Lys-Gln-Gln-Asp-Ala-Gln-Ala-Ser-Lys-Asn-Asn-Phe-Gly-Thr-30 Glu-Phe-Gly-Ser-Glu-Thr-Asn-Val-Gln-Glu-Val-Lys-Gln-Gln-Asn-45 Ala-Gln-Ala-Ala-Asn-Lys-Ser-Gln-Asn-Ala-Gln-Ala-Ser-Lys-60 Asn-Asn-Phe-Gly-Thr-Glu-Phe-Ala-Ser-Glu-Thr-Ser-Ala-Gln-Glu-75 Val-Arg-Gln-Gln-Asn-Ala-Gln-Ala-Gln-Lys-Lys-Asn-Gln-Asn-90 Ser-Gly-Lys-Tyr-Gln-Gly-COOH. The primary sequence of the B-protein contains a large internal duplication (residues 17 to 50 and 52 to 85), and shows significant sequence homology with the A- and C-proteins, the other major proteins degraded during B. megaterium spore germination.