JBC, Vol. 250, Issue 19, 7647-7655, Oct, 1975
Calcium-binding protein of bovine intestine. The complete amino acid sequence
W. Y. Huang, D. V. Cohn, J. W. Hamilton, C. Fullmer and R. H. Wasserman
The amino acid sequence for vitamin D-dependent bovine intestinal calcium
binding protein has been established. It contains 85 amino acids in a
single chain and lacks cysteine, tryptophan, methionine, histidine, and
arginine. The NH2-terminal lysine is blocked by an N-acetyl group.
Enzymatic digestion with trypsin, chymotrypsin, and pepsin yielded a number
of peptides which were purified by two-dimensional high voltage paper
electrophoresis. These peptides were examined by end group analysis and
sequenced by the dansyl procedure. The absence of tryptophan permitted by a
single cleavage of the molecule by N-bromosuccinimide at the tyrosine
residue at position 8 and the larger fragment was subjected to automated
Edman degradation. By these means, the following sequence was established:
N-Ac-Lys-Gln-Ser-Pro-Leu-Glu-Tyr-Ala-Ala-Glu-Lys-Ser-Ile-Gln-Lys-Glu-Ile-G
lu-Lys-Gly-Phe-Phe-Lys-Gln-Leu-Leu-Val-Ser-Val-Gln-Lys-Ala-Gly-Asp-Lys-Glu
-Ser-Leu-Gln-Pro-Leu-Phe-Thr-Leu-Leu-Lys-Ser-Gly-Pro-Glu-Glu-Asn-Leu-Lys-G
lu-Ser-Gln-Asn-Gly-Pro-Asp-Leu-Ls7-Ser-Gly-Pro-Gly-Asn-Asp-Leu-Glu-Glu-Lys
-Gly-Thr-Asp-Val-Phe-Ser-Leu-Lys-Gln. Microheterogeneity may exist in the
molecule at residue 76 in which position threonine may be replaced by
serine. Comparison of the sequence of calcium-binding protein to the "test"
sequence of Tufty and Kretsinger ((1975) Science 187, 167-169) proposed to
identify E-F hands in muscle proteins suggests that intestinal
calcium-binding protein may likewise contain one or possibly two E-F hands
which could account for calcium-binding property. Dayhoff alignment scores,
however, calculated for calcium-binding protein against nine E-F hands in
muscle proteins parvalbumin, troponin and alkali light chains do not
indicate that intestinal calcium-binding protein is homologous to these
muscle protein chains.