This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ciaccio, C. Articles by Coletta, M. Search for Related Content PubMed PubMed Citation Articles by Ciaccio, C. Articles by Coletta, M.

Proton Linkage for CO Binding and Redox Properties of Bovine Lactoperoxidase

Chiara Ciaccio ^*, Giampiero De Sanctis , Stefano Marini ^*, Federica Sinibaldi ^*, Roberto Santucci ^*, Alessandro Arcovito , Andrea Bellelli , Elena Ghibaudi , Pia Ferrari Rosa  and Massimo Coletta ^*

^* Department of Experimental Medicine and Biochemical Sciences, Università di Tor Vergata, I-00133 Rome, Italy; Department of Molecular, Cellular and Animal Biology, Università di Camerino, I-62032 Camerino (MC), Italy; CNR Institute of Molecular Biology and Pathology, and Department of Biochemical Sciences "Alessandro Rossi Fanelli", Università "La Sapienza", I-00185 Rome, Italy; and Department of I.F.M. Chemistry, Università di Torino, I-10125, Turin, Italy

Correspondence: Address reprint requests to Professor Massimo Coletta, Dept. of Experimental Medicine and Biochemical Sciences, Università di Tor Vergata, Via Montpellier 1, I-00133 Rome, Italy. Tel: +39-06-72596365; Fax: +39-06-72596353; E-mail: coletta{at}seneca.uniroma2.it.

The pH-dependence of redox properties and of CO binding to bovine lactoperoxidase has been investigated over the range between 2 and 11. The pH-dependence of redox potentials shows a biphasic behavior, suggesting the existence of (at least) two redox-linked groups, which change their pK_a values upon reduction. These values are in close agreement with those observed to play a relevant role in the modulation of CO binding to ferrous bovine lactoperoxidase. They have been tentatively attributed to Arg-372 and His-226, which are located on the distal side of the heme pocket of lactoperoxidase. A complete and unequivocal description of the proton-linked behavior of bovine lactoperoxidase requires, however, three residues, which are redox linked and relevant for the modulation of CO binding. The rate constant for CO binding to bovine lactoperoxidase is slower than what is reported for most hemoproteins, suggesting that these two residues, Arg-372 and His-226, are representing a severe barrier for the access of exogenous ligands to the heme. This aspect has been further investigated by fast kinetics following laser photolysis, trying to obtain information on the ligand binding pathway and on the energy barriers.