Nash A R, Fisher W K, Thompson E O
Aust J Biol Sci. 1976 Mar;29(1-2):73-97.
The amino acid sequence of the alpha-chain of the principal haemoglobin from the shark, H. portusjacksoni has been determined. The chain has 148 residues and is acetylated at the amino terminal. The soluble peptides obtained by tryptic and chymotryptic digestion of the protein or its cyanogen bromide fragments were isolated by gel filtration, paper ionophoresis and paper chromatography. The amino acid sequences were determined by the dansyl-Edman procedure. The insoluble "core" peptide from the tryptic digestion contained 34 residues and required cleavage by several prosteases before the sequence was established. Compared with human alpha-chain there are 88 amino acid differences including the additional seven residues which appear on the amino terminal of the shark chain. There is also one deletion and one insertion. The chain contains no tryptophan but has four cysteinyl residues which is the highest number of such residues recorded for a vertebrate globin. In the alpha1beta1 contact sites there are four changes in the oxyhaemoglobin form and six deoxy form. Nine of the 16, alpha1beta1 contact sites show variation while three of the haem contact sites have changed in comparison to the residues known to be involved in these interactions in horse haemoglobin alpha-chain. Use of the sequence data to estimate a time of divergence of the shark from the main vertebrate line yielded the value of 410 +/- 46 million years. The data, in general, support the palaeontological view that bony fishes arose before the elasmobranchs.
已确定鲨鱼杰克逊港噬人鲨主要血红蛋白α链的氨基酸序列。该链有148个残基，氨基末端被乙酰化。通过凝胶过滤、纸电泳和纸色谱法分离了通过胰蛋白酶和糜蛋白酶消化该蛋白质或其溴化氰片段得到的可溶性肽。氨基酸序列通过丹磺酰-埃德曼法测定。胰蛋白酶消化产生的不溶性“核心”肽含有34个残基，在确定序列之前需要用几种蛋白酶进行切割。与人类α链相比，有88个氨基酸差异，包括鲨鱼链氨基末端额外的七个残基。还有一个缺失和一个插入。该链不含色氨酸，但有四个半胱氨酰残基，这是脊椎动物球蛋白中此类残基记录的最高数量。在α1β1接触位点，氧合血红蛋白形式有四个变化，脱氧形式有六个变化。与马血红蛋白α链中已知参与这些相互作用的残基相比，16个α1β1接触位点中有9个显示出变异，3个血红素接触位点发生了变化。利用序列数据估计鲨鱼与主要脊椎动物谱系的分化时间，得出的值为4.10±0.46亿年。总体而言，这些数据支持古生物学观点，即硬骨鱼出现在板鳃亚纲之前。
