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Protein conformations and their stability
Author(s) -
Pace C. N.
Publication year - 1983
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/bf02660210
Subject(s) - globular protein , chemistry , crystallography , protein structure , peptide , protein folding , native state , amino acid , peptide bond , side chain , kinetics , stereochemistry , biochemistry , organic chemistry , polymer , physics , quantum mechanics
Our understanding of the conformations of proteins and their stability has increased substantially in recent years. A reaction of considerable interest is native (N) ⇌ denatured (D) where N is the globular, native state of the protein which is now well defined as a result of numer‐ous structural determinations by X‐ray diffraction studies, and D represents unfolded, denatured states of the protein whose structure depends on the denaturant used to promote unfolding. Through experimental studies much is known about the kinetics, thermody‐namics, and mechanism of this reaction. For example, it is known that the free energy change for this reaction under physiological conditions, ΔG D , is between 3 and 15 kcal/mol for a fairly wide range of globular proteins. Thus, the globular conformation which is absolutely essential for the biological function is only marginally stable. In addition, these ΔG D values are remarkably sensitive to small changes in the structure of the protein. It has been shown that single amino acid substitutions can dramatically increase or decrease ΔG D values and some substitutions surely lead to unfolding of the polypeptide chain. Most chemical alterations in the structure of a protein, e.g., cleavage of a peptide bond, or modification of an amino acid side chain, lead to decreases, often sizable, in the confor‐mational stability. The remarkably low conformational stability of globular proteins is important, in part, because many properties of the protein, e.g., solubility and proteolytic digestibility, change sub‐stantially when the protein unfolds. Recent developments in these areas of interest to protein chemists and food scientists are illus‐trated and discussed.