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Oligomeric Complexes (oligomeric + complex)
Selected AbstractsThe oligomeric state and stability of the mannitol transporter, EnzymeIImtl, from Escherichia coli: A fluorescence correlation spectroscopy studyPROTEIN SCIENCE, Issue 8 2006Gertjan Veldhuis Abstract Numerous membrane proteins function as oligomers both at the structural and functional levels. The mannitol transporter from Escherichia coli, EnzymeIImtl, is a member of the phosphoenolpyruvate-dependent phosphotransferase system. During the transport cycle, mannitol is phosphorylated and released into the cytoplasm as mannitol-1-phosphate. Several studies have shown that EIImtl functions as an oligomeric species. However, the oligomerization number and stability of the oligomeric complex during different steps of the catalytic cycle, e.g., substrate binding and/or phosphorylation of the carrier, is still under discussion. In this paper, we have addressed the oligomeric state and stability of EIImtl using fluorescence correlation spectroscopy. A functional double-cysteine mutant was site-specifically labeled with either Alexa Fluor 488 or Alexa Fluor 633. The subunit exchange of these two batches of proteins was followed in time during different steps of the catalytic cycle. The most important conclusions are that (1) in a detergent-solubilized state, EIImtl is functional as a very stable dimer; (2) the stability of the complex can be manipulated by changing the intermicellar attractive forces between PEG-based detergent micelles; (3) substrate binding destabilizes the complex whereas phosphorylation increases the stability; and (4) substrate binding to the phosphorylated species partly antagonizes the stabilizing effect. [source] Identification of Lmo1 as part of a Hox-dependent regulatory network for hindbrain patterningDEVELOPMENTAL DYNAMICS, Issue 9 2007Christelle Matis Abstract The embryonic functions of Hox proteins have been extensively investigated in several animal phyla. These transcription factors act as selectors of developmental programmes, to govern the morphogenesis of multiple structures and organs. However, despite the variety of morphogenetic processes Hox proteins are involved in, only a limited set of their target genes has been identified so far. To find additional targets, we used a strategy based upon the simultaneous overexpression of Hoxa2 and its cofactors Pbx1 and Prep in a cellular model. Among genes whose expression was upregulated, we identified LMO1, which codes for an intertwining LIM-only factor involved in protein,DNA oligomeric complexes. By analysing its expression in Hox knockout mice, we show that Lmo1 is differentially regulated by Hoxa2 and Hoxb2, in specific columns of hindbrain neuronal progenitors. These results suggest that Lmo1 takes part in a Hox paralogue 2,dependent network regulating anteroposterior and dorsoventral hindbrain patterning. Developmental Dynamics 236:2675,2684, 2007. © 2007 Wiley-Liss, Inc. [source] AAA+ superfamily ATPases: common structure,diverse functionGENES TO CELLS, Issue 7 2001Teru Ogura The AAA+ superfamily of ATPases, which contain a homologous ATPase module, are found in all kingdoms of living organisms where they participate in diverse cellular processes including membrane fusion, proteolysis and DNA replication. Recent structural studies have revealed that they usually form ring-shaped oligomers, which are crucial for their ATPase activities and mechanisms of action. These ring-shaped oligomeric complexes are versatile in their mode of action, which collectively seem to involve some form of disruption of molecular or macromolecular structure; unfolding of proteins, disassembly of protein complexes, unwinding of DNA, or alteration of the state of DNA,protein complexes. Thus, the AAA+ proteins represent a novel type of molecular chaperone. Comparative analyses have also revealed significant similarities and differences in structure and molecular mechanism between AAA+ ATPases and other ring-shaped ATPases. [source] Can radical cations of the constituents of nucleic acids be formed in the gas phase using ternary transition metal complexes?,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2005Sheena Wee Electrospray ionization (ESI) tandem mass spectrometry (MS/MS) of ternary transition metal complexes of [M(L3)(N)]2+ (where M,=,copper(II) or platinum(II); L3,=,diethylenetriamine (dien) or 2,2,:6,,2,-terpyridine (tpy); N,=,the nucleobases: adenine, guanine, thymine and cytosine; the nucleosides: 2,deoxyadenosine, 2,deoxyguanosine, 2,deoxythymine, 2,deoxycytidine; the nucleotides: 2,deoxyadenosine 5,-monophosphate, 2,deoxyguanosine 5,-monophosphate, 2,deoxythymine 5,-monophosphate, 2,deoxycytidine 5,-monophosphate) was examined as a means of forming radical cations of the constituents of nucleic acids in the gas phase. In general, sufficient quantities of the ternary complexes [M(L3)(N)]2+ could be formed for MS/MS studies by subjecting methanolic solutions of mixtures of a metal salt [M(L3)X2] (where M,=,Cu(II) or Pt(II); L3,=,dien or tpy; X,=,Cl or NO3) and N to ESI. The only exceptions were thymine and its derivatives, which failed to form sufficient abundances of [M(L3)(N)]2+ ions when: (a) M,=,Pt(II) and L3,=,dien or tpy; (b) M,=,Cu(II) and L3,=,dien. In some instances higher oligomeric complexes were formed; e.g., [Pt(tpy)(dG)n]2+ (n,=,1,13). Each of the ternary complexes [M(L3)(N)]2+ was mass-selected and then subjected to collision-induced dissociation (CID) in a quadrupole ion trap. The types of fragmentation reactions observed for these complexes depend on the nature of all three components (metal, auxiliary ligand and nucleic acid constituent) and can be classified into: (i) a redox reaction which results in the formation of the radical cation of the nucleic acid constituent, N+.; (ii) loss of the nucleic acid constituent in its protonated form; and (iii) fragmentation of the nucleic acid constituent. Only the copper complexes yielded radical cations of the nucleic acid constituent, with [Cu(tpy)(N)]2+ being the preferred complex due to suppression, in this case, of the loss of the nucleobase in its protonated form. The yields of the radical cations of the nucleobases from the copper complexes follow the order of their ionization potentials (IPs): G (lowest IP),>,A,>,C,>,T (highest IP). Sufficient yields of the radical cations of each of the nucleobases allowed their CID reactions (in MS3 experiments) to be compared to their even-electron counterparts. Copyright © 2005 John Wiley & Sons, Ltd. [source] | |||||||||||||