Covalent complex of microperoxidase with a 21-residue synthetic peptide as a maquette for low-molecular-mass redox proteins.
Here we report the structural and functional characterization of a covalent complex (MKP) obtained by cross-linking microperoxidase (Mp), the haem-undecapeptide obtained by the peptic digestion of cytochrome c, with a 21-residue synthetic peptide (P21) analogous to the S-peptide of the RNase A. The covalent complex has been prepared by introducing a disulphide bond between Cys-1 of P21 and Lys-13 of Mp, previously modified with a thiol-containing reagent. On formation of the complex (which is a monomer), the helical content of P21 increases significantly. The results obtained indicate that His-13 of P21 co-ordinates to the sixth co-ordination position of the haem iron, thus leading to the formation of a complex characterized by an equilibrium between an 'open' and a 'closed' structure, as confirmed by molecular dynamics simulations. Under acidic pH conditions, where His-13 of P21 is loosely bound to the haem iron ('open' conformation), MKP displays appreciable, quasi-reversible electrochemical activity; in contrast, at neutral pH ('closed' conformation) electrochemical behaviour is negligible, indicating that P21 interferes with the electron-transfer properties typical of Mp. On the whole, MKP is a suitable starting material for building a miniature haem system, with interesting potential for application to biosensor technology.
Ippoliti
R
R
Department of Biochemical Sciences 'A. Rossi-Fanelli', University of Rome La Sapienza, P. le Aldo Moro 5, 00185 Rome, Italy.
Picciau
A
A
Santucci
R
R
Antonini
G
G
Brunori
M
M
Ranghino
G
G
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D003198:Computer Simulation; D003432:Cross-Linking Reagents / Q000378:metabolism; D004563:Electrochemistry; D004579:Electron Transport; D006420:Hemeproteins / Q000737:chemistry; D007093:Imidazoles / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D010544:Peroxidases / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D015202:Protein Engineering; D017433:Protein Structure, Secondary; D012259:Ribonuclease, Pancreatic / Q000737:chemistry; D013053:Spectrophotometry
D000596:Amino Acids; D003432:Cross-Linking Reagents; D006420:Hemeproteins; D007093:Imidazoles; D010446:Peptide Fragments; C060871:ribonuclease A S-peptide; C029899:imidazole; D010544:Peroxidases; C021799:microperoxidase; D012259:Ribonuclease, Pancreatic