Furuta H, Kajita A
Biochemistry. 1983 Feb 15;22(4):917-22. doi: 10.1021/bi00273a032.
The complete amino acid sequence of a dimeric hemoglobin (HbI) from the marine bivalve mollusc Anadara broughtonii was determined by sequencing of the intact chain and peptide fragments produced by cleavage at two asparaginylglycine bonds and at methionyl, arginyl, and tryptophanyl residues. The clam hemoglobin consists of two identical polypeptide chains. The globin chain has 146 amino acid residues with a proline at the NH2 terminus and a leucine at the COOH terminus. The calculated molecular mass of the native hemoglobin was 32945 daltons. The clam hemoglobin contains only two histidine residues, which correspond to the distal and proximal heme-linked positions. Compared with human beta chain, an additional segment of seven residues is present in the NH2-terminal region and also five less residues in the COOH-terminal region. Although such an amino-terminal elongation has been known to be characteristic of hemoglobins from the most primitive living vertebrates Cyclostomata, a very similar structure was found to occur in the hemoglobin from the primitive invertebrate arcid clam.
通过对完整链以及在两个天冬酰胺基甘氨酸键、甲硫氨酰基、精氨酰基和色氨酸残基处裂解产生的肽片段进行测序，确定了海洋双壳贝类软体动物江户明蛤中二聚体血红蛋白（HbI）的完整氨基酸序列。蛤血红蛋白由两条相同的多肽链组成。珠蛋白链有146个氨基酸残基，NH2末端为脯氨酸，COOH末端为亮氨酸。天然血红蛋白的计算分子量为32945道尔顿。蛤血红蛋白仅含有两个组氨酸残基，分别对应于与血红素相连的远端和近端位置。与人类β链相比，NH2末端区域有一个额外的七个残基片段，COOH末端区域也少五个残基。尽管已知这种氨基末端延伸是最原始的现存脊椎动物圆口纲血红蛋白的特征，但在原始无脊椎动物蚶科蛤的血红蛋白中也发现了非常相似的结构。
