Equilibrium mechanisms of length regulation in linear protein aggregates

✍ Scribed by Terence Wagenknecht; Victor A. Bloomfield

• Publisher: Wiley (John Wiley & Sons)
• Year: 1975
• Tongue: English
• Weight: 587 KB
• Volume: 14
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1975.360141106

✦ Synopsis

Abstract

Statistical thermodynamic theories have been developed in order to explore the consequences of two prominent models of length regulation in linear protein aggregates: the length‐determining factor model and the cumulated strain model. In the former, the possibility that the final subunit is bound with extra stability has been incorporated. Calculations explore the dependence of the sharpness of the onset of extensive polymerization, and the breadth, shape, and most probable value of the distribution as functions of concentrations of template and polymerizing subunit, of subunit association constant, of the strain free energy, and of the maximum length and extra stability of the last subunit in the length‐determining factor model. Numerical calculations are made with particular reference to the parameters of bacteriophage T4 tail‐core polymerization. Both models predict suitably narrow length distributions with plausible values of the thermodynamic parameters. The length‐determining factor model may exhibit highly cooperative behaviour, with either fully polymerized or very short aggregates being observed as the product K[C] of association constant and free monomer constant is varied. This cooperativity is accentuated as binding of the final subunit becomes more stable. Species of intermediate length will be observable only if the length‐determining factor is shortened. In the cumulated strain model, if K[C] is lowered at constant strain free energy per subunit, shorter aggregates will be observed; but increasing K[C] will not yield appreciably longer polymers. As [C] is lowered, the distribution will remain narrow.