ABSTRACT
Several factors that may contribute to the stabilization of the helical structure in proteins, detected in studies made on short synthetic peptides, have been reported. Some of them are: presence of alanine or leucine, ionic-pair bonding, stabilization of the helical dipole moment by appropriate charges at the helix N- and C-caps, and aromatic interactions of amino acids located at positions i, i + 4. An analysis of 54 helical structures from 12 proteins showed that all these stabilizing factors were also present in proteins, but the influence of any of them had a different weight, according to the distribution of the hydrophobic and hydrophilic amino acid residues in the helical sequence. The role of non-sequence depending interactions in helical stability, such as presence of disulfide bridges, or bonding of helical residues to substrate and/or cofactors, was also analysed
Subject(s)
Alanine/physiology , Amino Acids/physiology , Enzyme Stability/physiology , Leucine/physiology , Muramidase/ultrastructure , Pancreatic Hormones/physiology , Protein Structure, SecondaryABSTRACT
Since the determination of the tertiary structure by X-ray crystallography has been achieved only for a limited number of proteins, alternative approaches are being sought. In this article, the use of secondary structure prediction and of molecular modeling is discussed. Several examples are analyzed in detail