On the molecular size of thymosins

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Abstract
The immunoregulatory polypeptide prothymosin α and its biologically active N‐terminal fragment thymosin α1m, with relative molecular masses of 12 500 and 3108 respectively, were found to behave as oligomers (trimers to hexamers) in gel‐filtration measurements. This phenomenon of an apparent association of polypeptides has been reported for other thymosins — parathymosin α, thymosin β4 and thymosin β10. In contrast, sedimentation equilibrium ultracentrifugation shows that thymosin α1 is a monomer with a relative molecular mass of 3000±200. Measurement of the diffusion coefficient as 221 μm2/s suggests that the molecule is approximately spherical. The implications for the molecular species of prothymosin α, parathymosin α, and β‐thymosins are discussed.