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Biomedical subjects

S Rackovsky

Publications and source records attributed to S Rackovsky.

22 records · Page 2Linked to original sources
PubMed1984

On the redox conformational change in cytochrome c.

The relationship between the crystal structures of oxidized and reduced tuna cytochrome c has been reexamined by a superposition method motivated by recent studies of the cytochrome c-cytochrome c peroxidase complex. It is shown that the observed structural changes precisely reflect the binding face suggested by chemical modification studies. It is further suggested that the large observed motion of lysine-27 and a smaller overall motion of the two binding edges constitute a redox binding-affinity switch and that the driving force for the conformational change of the protein is provided by the internal conformational change and charge redistribution of the heme, which cause it to tilt, under the influence of covalent and nonbonded interactions, within its protein envelope. A picture is presented of the molecule as an electron storage/transfer machine with three elements--a binding module, an electron storage module, and a conformational energy-storage module.

Animals↗
PubMed1977

Hydrophobicity, hydrophilicity, and the radial and orientational distributions of residues in native proteins.

The radial distributions of the Calpha and side-chain atoms in a sample of 13 native proteins have been examined. It is found that there are substantial differences in behavior between different atoms of the same amino acid. In particular, the Calpha atoms of polar residues show no particular preference for being far from the center of mass. In light of these results, a new criterion for hydrophobicity and hydrophilicity is proposed--namely, the orientational preference of the side chain. The distribution of this property is shown, and it is suggested that this provides a basis for incorporating hydrophobic interactions into a protein folding algorithm.

Amino Acids↗
PubMedDate not supplied

Influence of ordered backbone structure on protein folding. A study of some simple models.

Four series of model molecules, each of which contains a coil section and one or two sections of fixed ordered backbone structure, have been examined to locate their low-energy conformations in water. The four series are: helix-coil, helix-coil-helix, extended-coil, and extended-coil-extended. In each series, the length of the coil is allowed to vary from four to ten residues, while the nuclei (ordered backbone structures) are held fixed at six residues. By comparing these molecules, it is observed that the low-energy conformations of those containing two nuclei can be regarded as being derived from low-energy conformations of molecules containing one nucleus. This suggests that folding of proteins containing preformed nuclei proceeds through interactions between the nuclei and adjacent non-regular sections of the chain rather than between nuclei. It is also observed that helices are better promoters of globularity than extended strands. These results are compared with those from recent studies of various aspects of protein folding.

Models, Molecular↗