Abstract
The hemoglobin of the Great Crested Newt (Triturus cristatus), an animal maintaining the gas exchange to about 85% through the skin, consists of a major (HbM = 65%) and a minor (Hbm = 35%) component. The primary structures of the four chains are presented. They could be separated by reversed-phase HPLC and were cleaved with trypsin and additionally by acid hydrolysis. Both the native chains and their peptides were sequenced by liquid and gas phase sequenators. At the N-terminus the alpha M-chains are by one amino-acid residue longer and the beta M-chains by one residue shorter, resulting in a chain length of 142 and 145, respectively. The alpha m-chains are of normal length whereas in the beta m-chains the C-terminal histidine in position 146 is missing. Both alpha-chains differ by 50 residues (35.2%) and the beta-chains by 63 (43.2%). The alpha-chains were compared with those of other salamandroid hemoglobins. The difference to human hemoglobin is marked by 61 (43.3%) amino-acid substitutions in both alpha-chains and by 78 (53.4%) in both beta-chains. Numerous heme contacts and positions involved in the subunit interface are affected by replacements. The most interesting of them were studied by molecular modeling. The importance of the missing beta m-146(HC3)His and of the substitution of several amino-acid residues involved in the binding of organic phosphates is discussed with respect to the reduced Bohr effect of Triturus cristatus hemoglobin.
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