title: Functional interaction of phospholipid hydroperoxide glutathione peroxidase with sperm mitochondrion-associated cysteine-rich protein discloses the adjacent cysteine motif as a new substrate of the selenoperoxidase.
abstract: The mitochondrial capsule is a selenium- and disulfide-rich structure enchasing the outer mitochondrial membrane of mammalian spermatozoa. Among the proteins solubilized from the sperm mitochondrial capsule, we confirmed, by using a proteomic approach, the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) as a major component, and we also identified the sperm mitochondrion-associated cysteine-rich protein (SMCP) and fragments/aggregates of specific keratins that previously escaped detection (Ursini, F., Heim, S., Kiess, M., Maiorino, M., Roveri, A., Wissing, J., and Flohé, L. (1999) Science 285, 1393-1396). The evidence for a functional association between PHGPx, SMCP, and keratins is further supported by the identification of a sequence motif of regularly spaced Cys-Cys doublets common to SMCP and high sulfur keratin-associated proteins, involved in bundling hair shaft keratin by disulfide cross-linking. Following the oxidative polymerization of mitochondrial capsule proteins, catalyzed by PHGPx, two-dimensional redox electrophoresis analysis showed homo- and heteropolymers of SMCP and PHGPx, together with other minor components. Adjacent cysteine residues in SMCP peptides are oxidized to cystine by PHGPx. This unusual disulfide is known to drive, by reshuffling oxidative protein folding. On this basis we propose that oxidative polymerization of the mitochondrial capsule is primed by the formation of cystine on SMCP, followed by reshuffling. Occurrence of reshuffling is further supported by the calculated thermodynamic gain of the process. This study suggests a new mechanism where selenium catalysis drives the cross-linking of structural elements of the cytoskeleton via the oxidation of a keratin-associated protein.
authors.affiliation: Department of Biological Chemistry, University of Padova, Italy.
authors.forename: Matilde
authors.initials: M
authors.lastname: Maiorino
authors.forename: Antonella
authors.initials: A
authors.lastname: Roveri
authors.forename: Louise
authors.initials: L
authors.lastname: Benazzi
authors.forename: Valentina
authors.initials: V
authors.lastname: Bosello
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Mauri
authors.forename: Stefano
authors.initials: S
authors.lastname: Toppo
authors.forename: Silvio C E
authors.initials: SC
authors.lastname: Tosatto
authors.forename: Fulvio
authors.initials: F
authors.lastname: Ursini
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003545:Cysteine / Q000737:chemistry; D003599:Cytoskeleton / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005979:Glutathione Peroxidase / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007633:Keratins / Q000737:chemistry; D008297:Male; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D009195:Peroxidase / Q000737:chemistry*; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D010743:Phospholipids / Q000378:metabolism; D011108:Polymers / Q000737:chemistry; D011485:Protein Binding; D017510:Protein Folding; D051381:Rats; D012643:Selenium / Q000737:chemistry*; D051140:Selenoproteins / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D013094:Spermatozoa / Q000378:metabolism*; D013379:Substrate Specificity; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D003432:Cross-Linking Reagents; D004220:Disulfides; D010455:Peptides; D010743:Phospholipids; D011108:Polymers; C099545:SMCP protein, rat; D051140:Selenoproteins; D007633:Keratins; D006861:Hydrogen Peroxide; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D009195:Peroxidase; D005979:Glutathione Peroxidase; D012643:Selenium; D003545:Cysteine; D010100:Oxygen