The compact structure of globular proteins is predominantly determined by hydrophobic interactions of bulky nonpolar side groups. Both from the point of view of modelling this main feature of globular protein structure, and also from the viewpoint of their evolutionary origin, it is of significant interest to clarify whether water-soluble random copolymers of polar and non-polar amino acids are able to form compact structures. Recently Miller and his collaborators proposed [1] using random copolymer gel-chromatography to isolate fractions with a compact structure and obtained evidence for the presence of such fractions in random copolymers consisting of Ala, Glu and Lys. It has been shown in a previous paper [2] that a nonaggregating fraction can be isolated from random copolymers of Glu and Leu. The potentiometric titration curve of this fraction allowed one to presume the existence of a compact structure in a weakly ionized state. In the present communication it is reported that with a decrease of ionization of molecules of this fraction, they at first pass from a coil-like state into the helical with a subsequent intramolecular aggregation of helical regions, which may be of interest in the light of existing concepts on the mechanism of globular protein self-organization [3 -5 ] .
[1]
Benno Hess,et al.
Analysis and simulation of biochemical systems
,
1972
.
[2]
G. Fasman,et al.
CONFORMATIONAL STUDIES ON SYNTHETIC POLY-ALPHA-AMINO ACIDS: FACTORS INFLUENCING THE STABILITY OF THE HELICAL CONFORMATION OF POLY-L-GLUTAMIC ACID AND COPOLYMERS OF L-GLUTAMIC ACID AND L-LEUCINE.
,
1964,
Biochemistry.
[3]
Polymerization in biological systems
,
1972
.
[4]
C B Anfinsen,et al.
The formation and stabilization of protein structure.
,
1972,
The Biochemical journal.
[5]
Miller Wg,et al.
Collapsed structure polymers. A scattergun approach to amino acid copolymers.
,
1974
.