Protein folding and protein evolution: common folding nucleus in different subfamilies of c-type cytochromes?
| Autor: | Ptitsyn Ob |
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| Rok vydání: | 1998 |
| Předmět: |
Models
Molecular Protein Folding Chloroplasts Heme binding Stereochemistry Protein Conformation Molecular Sequence Data Cytochrome c Group Heme Saccharomyces cerevisiae Biology Homology (biology) Evolution Molecular Structural Biology medicine Animals Amino Acid Sequence Horses Molecular Biology Conserved Sequence chemistry.chemical_classification Binding Sites Bacteria Sequence Homology Amino Acid Cytochrome c Amino acid Mitochondria Chloroplast Crystallography Kinetics medicine.anatomical_structure chemistry Helix biology.protein Protein folding Nucleus Sequence Alignment |
| Zdroj: | Journal of molecular biology. 278(3) |
| ISSN: | 0022-2836 |
| Popis: | Amino acid sequences of seven subfamilies of cytochromes c (mitochondrial cytochromes c, c1; chloroplast cytochromes c6, cf; bacterial cytochromes c2, c550, c551; in total 164 sequences) have been compared. Despite extensive homology within eukaryotic subfamilies, homology between different subfamilies is very weak. Other than the three heme-binding residues (Cys13, Cys14, His18, in numeration of horse cytochrome c) there are only four positions which are conserved in all subfamilies: Gly/Ala6, Phe/Tyr10, Leu/Val/Phe94 and Tyr/Trp/Phe97. In all 17 cytochromes c with known 3D-structures, these residues form a network of conserved contacts (6–94, 6–97, 10–94, 10–97 and 94–97). Especially strong is the contact between aromatic groups in positions 10 and 97, which corresponds to 13 interatomic contacts. As residues 6, 10 and residues 94, 97 are in (i, i + 4) and (i, i + 3) positions in the N and C-terminal helices, respectively, the above mentioned system of conserved contacts consists mainly of contacts between one turn of N-terminal helix and one turn of C-terminal helix. The importance of the contacts between interfaces of these helices has been confirmed by the existence of these contacts in both equilibrium and kinetic molten globule-like folding intermediates, as well as by mutational evidence that these contacts are involved in tight packing between the N and C-helices. Since these four residues are not involved in heme binding and have no other apparent functional role, their conservation in highly diverged cytochromes c suggests that they are of a critical importance for protein folding. The author assumes that they are involved in a common folding nucleus of all subfamilies of c-type cytochromes. |
| Databáze: | OpenAIRE |
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