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Limited proteolysis of cytochrome c in trifluoroethanol
Author(s) -
Fontana Angelo,
Zambonin Marcello,
De Filippis Vincenzo,
Bosco Manuela,
de Laureto Patrizia Polverino
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)00237-4
Subject(s) - thermolysin , chemistry , proteolysis , cytochrome c , peptide , peptide bond , stereochemistry , protein secondary structure , protease , hemeprotein , protein structure , biochemistry , trypsin , enzyme , heme , mitochondrion
Horse heart cytochrome c is cleaved by thermolysin in 50% aqueous TFE (v/v) at neutral pH (25°C, 24 h) at the Gly 56 ‐Ile 57 peptide bond of the 104‐residue chain of the protein. Additional, but anyway minor, fragmentation at the Gly 45 ‐Phe 46 and Met 80 ‐Ile 81 peptide bonds is also observed. On the other hand, in buffer only and in the absence of TFE, cytochrome c is digested by thermolysin to numerous small peptides. Considering the broad substrate specificity of the TFE‐resistant thermolysin, clearly the conformational state of the protein substrate dictates the observed selective proteolysis. It is proposed that the highly helical secondary structure acquired by cytochrome c when dissolved in aqueous TFE hampers binding and adaptation of the protein substrate at the active site of the protease and that peptide bond fission occurs at flexible chain segments characterized by a low α‐helix propensity.