期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1971
卷号：68
期号：10
页码：2417-2420
DOI：10.1073/pnas.68.10.2417
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The complete amino-acid sequence of the 2.5S nerve growth factor from male-mouse submaxillary glands has been determined. The unambiguous alignment of peptides derived from tryptic, chymotryptic, thermolytic, and peptic digestion of S-carboxymethyl-, S-aminoethyl-, and native growth factor indicates that the primary subunit is composed of 118 amino acids, with amino-terminal serine and carboxyl-terminal arginine. The molecular weight of this subunit, calculated from the primary sequence, is 13,259. Thus, the native protein, which is composed of two of the subunits, has a molecular weight of 26,518. These values, as well as the final amino-acid composition, are in excellent agreement with those determined by direct measurement with undigested growth factor. The alignment of the three disulfide bonds, determined from a combination of peptic and thermolytic digestions, is I-IV, II-V, and III-VI. The latter two pairs are located in a closed loop of 14 amino acids, by virtue of the fact that half-cystinyl residues V and VI are separated by only a single residue in the linear sequence. Assignment of the side-chain amides showed that 7 of 11 aspartic acid residues and 2 of 8 glutamic acid residues are present as amides. This distribution of charged residues is entirely consistent with the observed isoelectric point of 9.3.
关键词：2.5S protein ; two subunits ; disulfide bonds ; enzymatic digestion
