title: Proton NMR study of chemically modified horse heart ferricytochrome c confirms the presence of histidine and lysine-ligated conformers in 30% acetonitrile solution.
abstract: Comparison of the 1H NMR spectra for guanidinated ferricyt c and chloro(terpyridine)platinum(II)-modified ferricyt c in 30% acetonitrile (ACN) solution with that for ferricyt c in 30% ACN is reported. The absence of the heme methyl proton resonances characteristic of the IV*-form (Lys-ligated) in the NMR spectrum of guanidinated ferricyt c in 30% ACN solution confirms that a lysine-ligated form of ferricyt c is produced in 30% ACN solution. The absence of the 8-methyl heme proton resonance of the V*-form in the NMR spectrum of chloro(terpyridine)platinum(II)-modified ferricyt c in 30% ACN solution demonstrates that a bis-His-ligated form of ferricyt c is produced in 30% ACN, not a hydroxide ligated form, as previously proposed. The revised assignment for the V* form of ferricyt c in mixed media explains differences between the exchange network we previously reported for ferricyt c in 30% ACN [Protein Sci. 10 (2001) 2291] as versus that reported by Dopner et al. at high pH [J. Am. Chem. Soc. 120 (1998) 11246]. Lys- and His-ligated forms are known to be produced in the presence of denaturants in protein folding studies of ferricyt c. Consequently, the exchange network between these non-native forms of ferricyt c in 30% ACN may have biological relevance for ferricyt c folding.
authors.affiliation: Department of Chemistry and Chemical Biology, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, USA.
authors.forename: Sivashankar G
authors.initials: SG
authors.lastname: Sivakolundu
authors.forename: Patricia Ann
authors.initials: PA
authors.lastname: Mabrouk
mesh_terms: D000097:Acetonitriles / Q000737:chemistry; D000818:Animals; D003574:Cytochrome c Group / Q000032:analysis / Q000737:chemistry*; D006146:Guanidines / Q000737:chemistry; D006418:Heme / Q000737:chemistry; D006639:Histidine / Q000737:chemistry*; D006736:Horses; D008024:Ligands; D008239:Lysine / Q000737:chemistry*; D008929:Mitochondria, Heart / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D009944:Organoplatinum Compounds / Q000737:chemistry*; D011487:Protein Conformation; D011522:Protons; D012996:Solutions
chemical_list: D000097:Acetonitriles; D003574:Cytochrome c Group; D006146:Guanidines; D008024:Ligands; D009944:Organoplatinum Compounds; D011522:Protons; D012996:Solutions; D006418:Heme; D006639:Histidine; C021975:chloroterpyridineplatinum(II); D008239:Lysine; C032159:acetonitrile