The structural and redox properties of a non-covalent complex reconstituted upon mixing two non-contiguous fragments of horse cytochrome c, the residues 1 - 38 heme-containing N-fragment with the residues 57 - 104 C-fragment, have been investigated. With respect to native cyt c, the complex lacks a segment of 18 residues, corresponding, in the native protein, to an omega ( W)loop region. The fragment complex shows compact structure, native-like alpha-helix content but a less rigid atomic packing and reduced stability with respect to the native protein. Structural heterogeneity is observed at pH 7.0, involving formation of an axially misligated low-spin species and consequent partial displacement of Met80 from the sixth coordination position of the heme-iron. Spectroscopic data suggest that a lysine ( located in the Met80-containing loop, namely Lys72, Lys73, or Lys79) replaces the methionine residue. The residues 1 - 38/57 - 104 fragment complex shows an unusual biphasic alkaline titration characterized by a low (pK(a1)= 6.72) and a high pK(a)-associated state transition (pK(a2)= 8.56); this behavior differs from that of native cyt c, which shows a monophasic alkaline transition ( pK(a)= 8.9). The data indicate that the 40s Omega-loop plays an important role in the stability of cyt c and in ensuring a correct alkaline conformational transition of the protein.

Caroppi, P., Sinibaldi, F., Santoni, E., Howes, B., Fiorucci, L., Ferri, T., et al. (2004). The 40s Omega-loop plays a critical role in the stability and the alkaline conformational transition of cytochrome c. JBIC, 9(8), 997-1006 [10.1007/s00775-004-0601-9].

The 40s Omega-loop plays a critical role in the stability and the alkaline conformational transition of cytochrome c

SINIBALDI, FEDERICA;FIORUCCI, LAURA;SANTUCCI, ROBERTO
2004

Abstract

The structural and redox properties of a non-covalent complex reconstituted upon mixing two non-contiguous fragments of horse cytochrome c, the residues 1 - 38 heme-containing N-fragment with the residues 57 - 104 C-fragment, have been investigated. With respect to native cyt c, the complex lacks a segment of 18 residues, corresponding, in the native protein, to an omega ( W)loop region. The fragment complex shows compact structure, native-like alpha-helix content but a less rigid atomic packing and reduced stability with respect to the native protein. Structural heterogeneity is observed at pH 7.0, involving formation of an axially misligated low-spin species and consequent partial displacement of Met80 from the sixth coordination position of the heme-iron. Spectroscopic data suggest that a lysine ( located in the Met80-containing loop, namely Lys72, Lys73, or Lys79) replaces the methionine residue. The residues 1 - 38/57 - 104 fragment complex shows an unusual biphasic alkaline titration characterized by a low (pK(a1)= 6.72) and a high pK(a)-associated state transition (pK(a2)= 8.56); this behavior differs from that of native cyt c, which shows a monophasic alkaline transition ( pK(a)= 8.9). The data indicate that the 40s Omega-loop plays an important role in the stability of cyt c and in ensuring a correct alkaline conformational transition of the protein.
Pubblicato
Rilevanza internazionale
Articolo
Esperti anonimi
Settore BIO/10
English
Con Impact Factor ISI
Cytochrome c; Fragment complex; Intermediate state; Loop regions
Caroppi, P., Sinibaldi, F., Santoni, E., Howes, B., Fiorucci, L., Ferri, T., et al. (2004). The 40s Omega-loop plays a critical role in the stability and the alkaline conformational transition of cytochrome c. JBIC, 9(8), 997-1006 [10.1007/s00775-004-0601-9].
Caroppi, P; Sinibaldi, F; Santoni, E; Howes, B; Fiorucci, L; Ferri, T; Ascoli, F; Smulevich, G; Santucci, R
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/34631
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