A radioimmunoassay for parathymosin.

Parathymosin, a polypeptide that is structurally related to prothymosin alpha, has been shown to block the in vivo immunoenhancing effects of prothymosin alpha (Haritos, A.A., Salvin, S.

Prothymosin alpha in human blood.

The major cross-reacting peptide in human plasma detected with a radioimmunoassay (RIA) for thymosin alpha 1 was identified as prothymosin alpha, based on its elution properties in gel-filtration chromatography and its amino acid composition after purification by HPLC. A small quantity (less than 10%) of the total cross-reacting material was recovered in fractions corresponding to lower molecular weight thymosin alpha 1-like peptides. The total quantity of cross-reacting material detected in human blood, expressed as thymosin alpha 1 equivalents, was 11-14 pmol/ml (approximately 90% was recovered in the leukocyte fraction, approximately 10% was in the plasma fraction, and 1-2% was in the erythrocyte fraction).

Simultaneous isolation and determination of prothymosin alpha, parathymosin alpha, thymosin beta 4, and thymosin beta 10.

A method was described for the isolation of peptides from rat thymus. Frozen, powdered tissue was suspended in boiling buffer to inactivate endogenous proteinases, the suspension was homogenized, and the peptides were isolated by a two-step procedure including gel filtration and purification by HPLC. The recoveries from rat thymus were, in micrograms per gram of whole tissue, 60-80 for prothymosin alpha, 50-80 for thymosin beta 4, and 20-30 for thymosin beta 10.

Primary structure of rat thymus prothymosin alpha.

The primary structure of prothymosin alpha from rat thymus, containing 113 amino acid residues, is reported as follows: (formula; see text) The sequence of the first 28 amino acids at the NH2 terminus is identical to that of calf thymosin alpha 1. The dicarboxylic amino acids, which account for nearly half of the total residues in prothymosin alpha, are largely clustered in the central portion of the polypeptide chain. The polypeptide contains no aromatic or sulfur-containing amino acids.

Thymosin alpha 11: a peptide related to thymosin alpha 1 isolated from calf thymosin fraction 5.

Two peptides related to thymosin alpha 1 have been isolated from preparations of calf thymosin fraction 5. One, lacking four amino acid residues at the COOH terminus, is designated des-(25-28)-thymosin alpha 1. The other, named thymosin alpha 11, contains seven additional amino acid residues at the COOH terminus.