Xia Q C, Chang D, Blacher R, Lai C Y
Arch Biochem Biophys. 1984 Nov 1;234(2):363-70. doi: 10.1016/0003-9861(84)90281-9.
The sequence of 96 amino acid residues from the COOH-terminus of the active subunit of cholera toxin, A1, has been determined as (sequence; see text) This is the largest fragment obtained by BrCN cleavage of the subunit A1 (Mr 23,000), and has previously been indicated to contain the active site for the adenylate cyclase-stimulating activity. Unequivocal identification of the COOH-terminal structure was achieved by separation and analysis of the terminal peptide after the specific chemical cleavage at the only cysteine residue in A1 polypeptide. The site of self ADP-ribosylation in the A1 subunit [C. Y. Lai, Q.-C. Xia, and P.T. Salotra (1983) Biochem. Biophys. Res. Commun. 116, 341-348] has now been identified as Arg-50 of this peptide, 46 residues removed from the COOH-terminus. The cysteine that forms disulfide bridge to A2 subunit in the holotoxin is at position 91.
霍乱毒素A1活性亚基羧基末端96个氨基酸残基的序列已确定为（序列见正文）。这是通过溴化氰裂解A1亚基（分子量23,000）得到的最大片段，先前已表明其含有刺激腺苷酸环化酶活性的活性位点。通过在A1多肽中唯一的半胱氨酸残基处进行特异性化学裂解后对末端肽进行分离和分析，实现了对羧基末端结构的明确鉴定。A1亚基中自ADP-核糖基化的位点[C.Y. Lai, Q.-C. Xia, and P.T. Salotra (1983) Biochem. Biophys. Res. Commun. 116, 341 - 348]现已确定为该肽段的精氨酸-50，距离羧基末端46个残基。在全毒素中与A2亚基形成二硫键的半胱氨酸位于第91位。
