Amino acid sequences of hordein polypeptides [barley, prolamin, carboxy-terminus]
1980
Schmitt, J.M. | Svendsen, I.
Total hordein and purified hordein polypeptides B1 and C2 have been analyzed by carboxypeptidase Y digestion and sequential Edman degradation. The carboxypeptidase Y-catalyzed release of amino acids reveals the sequence (Ile. Ser)-Ser-Met-Val-COOH for the carboxy terminus of the C2 polypeptide. The same amino acids, with an additional glycine, were released from a total hordein preparation. Glycine has previously been found in the carboxyterminal sequence -Gly-Val-COOH of the B1 polypeptide. The B1 polypeptide was blocked to Edman degradation. The C2 polypeptide yielded a single amino acid sequence: H(,2)N-Arg-Gln-Leu-Asn-Pro-Ser-Ser-Gln-Glu-Leu- X -Ser-Pro-Gln-Gln-Pro-Tyr-Leu-Gln-Gln-Pro-Tyr-Pro-Gln-Asn-... One sequence obtained from the total hordein preparation was identical with the C2 sequence and proved in addition glutamine to be the amino acid in position II. This sequence continued with the following residues: - X -Tyr-Leu-Glu- X -Gly-('31). More than one amino acid was identified at positions 7, 12, 15, 16, 27 and 31, suggesting the presence of several hordein polypeptides with very similar N-terminal sequences in the total hordein preparation. If the polymorphisms at these positions have arisen by amino acid substitutions, then seven of the twelve possible substitutions require two nucleotide changes in their codons. We tentatively propose that the amino termini of the hordein polypeptides accessible to Edman degradation are from an evolutionary point of view under functional constraint.
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