No abstract

We have analyzed the stability of the cytochrome c-cytochrome b5 and cytochrome c-cytochrome c oxidase complexes as a function of solvent stress. High concentrations of glycerol were used to displace the two equilibria. Glycerol promotes complex formation between cytochrome c and cytochrome b5 but inhibits that between cytochrome c and cytochrome c oxidase. The results with cytochrome b5 and cytochrome c were expected; the association of this complex is largely entropy driven. Our interpretation is that the cytochrome c-cytochrome b5 complex excludes water. The results with the cytochrome c oxidase and cytochrome c couple were not expected. We interpret them to mean that either glycerol is binding to the oxidase, thereby displacing the cytochrome c, or that water is required at this protein-protein interface. A requirement for substantial quantities of water at the interface of some protein complexes is logical but has been reported only once.

1974) Studies on the Structure and Formation during Spermatogenesis of the Sulfoglycerogalactolipid of Rat Testis. Can. I. Bioehem. 52, 689-697Structural studies on the major glycolipid of rat testis have confirmed our earlier identification of this compound as a 1-0-alkyl-2-0-acyl-glyce~yl-monogaIactoside sulfate. The acyl and alkyl groups are predominantly palmitoyl and palmityl groups, respectively. %he minor glycolipid found in the same tissue has been identified as the non-sulfated form of this glycolipid. Examination of the levels of the sulfoglycerogalactolipid in the testes of immature rats, hypophysectomized rats, and normal and sterile mice indicates that the majority of the compound is located in the germinal cells of the testis and that the primary spermatocytes are the earliest spermatogenic cells to contain high levels of the lipid. Galactolipid sulfotransferase also shows peak activity in the primary spermatocytes of rat testis. Kornblatt, M. J., Knapp, A., Levine, M., Schachter, H. &Murray, R. K. (1974) Studies on the Structure and Formation during Spermatogenesis of the Sulfoglycerogalactolipid of Rat Testis. Can. 1. Biochem. 52,689-697Cette ttude de la structure du principal glycolipide des testicules de rat confirme notre premibre identification de ce compos6 comme ttant le I-0-alkyl-2-0-acyl-glycCryl-monogalactoside sulfate. k s groupes acyle et alkyle sont surtout des groups palmitoyle et palmityle. Le glycolipide moins important retrouvt dans le meme tissu est la forme non sulfatte du principal glycolipide. L'examen des taux de sulfoglyc6rogalactolipide dans les testicules de rats non matures, de rats hypophysectomists, de souris sttriles et de souris nomales montre que la plus grande partie de ce cornperst se situe dans les cellules germinales des testicules et que les spermatocytes primaires ssnt les premieres cellules spermatogbnes i contenir des quantitts 6levtes de ce ligide. C'est aussi dans les spermatocytes primaires des testicules de rat que l'activitk de la galactolipide sulfotransftrase est la plus ClevCe.praduit par le journal] Introduction are, therefore, studying aspects of the structure We have recently reported (1 ) that the major and metabolism of this lipid in the mammalian glycolipid of rat testis is a sulfated glycerogalac-testis in an effort to estabiish its function in this tolipid, tentatively identified as a monoalkyl-tissue. In the present report, we present further monsacyl-glyceryl-monogdactoside sulfate. data on the structures of the sulfoglycerogalacIshiauka et al. (2,3) have reported the isolation tolipid of rat testis and of a related compound s f a similar compound from boar and guinea-found in rat testis as a minor component. Since pig testes and have established its structure to be a 1-0-alkyl-2-0-acyl-3-P(3'-sulfogalactosyl)-glycerol. This novel compound is present in substantial amounts in the testes of the rat, mouse, guinea pig, rabbit, pig, and we

For years it has been clear that plasminogen from different sources and enolase from different sources interact strongly. What is less clear is the nature of the structures required for them to interact. This work examines the interaction between canine plasminogen (dPgn) and Streptococcus pyogenes enolase (Str enolase) using analytical ultracentrifugation (AUC), surface plasmon resonance (SPR), fluorescence polarization, dynamic light scattering (DLS), isothermal titration calorimetry (ITC), and simple pull-down reactions. Overall, our data indicate that a non-native structure of the octameric Str enolase (monomers or multimers) is an important determinant of its surface-mediated interaction with host plasminogen. Interestingly, a non-native structure of plasminogen is capable of interacting with native enolase. As far as we can tell, the native structures resist forming stable mixed complexes.

Most enolases are homodimers. There are a few that are octamers, with the eight subunits arranged as a tetramer of dimers. These dimers have the same basic fold and same subunit interactions as are found in the dimeric enolases. The dissociation of the octameric enolase from S. pyogenes was examined, using NaClO4, a weak chaotrope, to perturb the quaternary structure. Dissociation was monitored by sedimentation velocity. NaClO4 dissociated the octamer into inactive monomers. There was no indication that dissociation of the octamer into monomers proceeded via formation of significant amounts of dimer or any other intermediate species. Two mutations at the dimer-dimer interface, F137L and E363G, were introduced in order to destabilize the octameric structure. The double mutant was more easily dissociated than was the wild type. Dissociation could also be produced by other salts, including tetramethylammonium chloride (TMACl) or by increasing pH. In all cases, no significant amounts of dimers or other intermediates were formed. Weakening one interface in this protein weakened the other interface as well. Although enolases from most organisms are dimers, the dimeric form of the S. pyogenes enzyme appears to be unstable.