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Multienzyme Complex (multienzyme + complex)
Selected AbstractsProtease inhibitors in bacteria: an emerging concept for the regulation of bacterial protein complexes?MOLECULAR MICROBIOLOGY, Issue 6 2006Wolfgang H. Schwarz Summary Serine protease inhibitors (serpins), the antagonists of serine proteases, were unknown in the bacterial kingdom until recently. Kang et al. in this issue of Molecular Microbiology report the cloning and functional analysis of the three serpin genes from the thermophilic anaerobic bacterium Clostridium thermocellum. Two of the serpins contain a dockerin module for location in the extracellular hydrolytic multienzyme complex, the cellulosome. The susceptibility of cellulosome to proteolytic degradation and the presence of a serine protease in the same complex provoke speculation that protease inhibitor/protease pairs could play hitherto unrecognized roles in protein stability and regulation in bacteria. [source] NMR structure of the enzyme GatB of the galactitol-specific phosphoenolpyruvate-dependent phosphotransferase system and its interaction with GatAPROTEIN SCIENCE, Issue 10 2006Laurent Volpon Abstract The phosphoenolpyruvate-dependent carbohydrate transport system (PTS) couples uptake with phosphorylation of a variety of carbohydrates in prokaryotes. In this multienzyme complex, the enzyme II (EII), a carbohydrate-specific permease, is constituted of two cytoplasmic domains, IIA and IIB, and a transmembrane channel IIC domain. Among the five families of EIIs identified in Escherichia coli, the galactitol-specific transporter (IIgat) belongs to the glucitol family and is structurally the least well-characterized. Here, we used nuclear magnetic resonance (NMR) spectroscopy to solve the three-dimensional structure of the IIB subunit (GatB). GatB consists of a central four-stranded parallel ,-sheet flanked by ,-helices on both sides; the active site cysteine of GatB is located at the beginning of an unstructured loop between ,1 and ,1 that folds into a P-loop-like structure. This structural arrangement shows similarities with other IIB subunits but also with mammalian low molecular weight protein tyrosine phosphatases (LMW PTPase) and arsenate reductase (ArsC). An NMR titration was performed to identify the GatA-interacting residues. [source] Active-site changes in the pyruvate dehydrogenase multienzyme complex E1 apoenzyme component from Escherichia coli observed at 2.32,Å resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2006Palaniappa Arjunan The first enzymatic component, E1 (EC 1.2.4.1), of the pyruvate dehydrogenase multienzyme complex (PDHc) utilizes thiamine diphosphate (ThDP) and Mg2+ as cofactors. The structure of a branched-chain-specific E1 apoenzyme from the heterotetrameric ,2,2 E1 family was recently reported and showed that disorder-to-order transformations in two active-site loops take place upon cofactor binding. To ascertain what effect the absence of cofactor may have in the homodimeric ,2Escherichia coli PDHc E1, the corresponding apoenzyme has been prepared and its three-dimensional structure determined and analyzed at 2.32,Å by crystallographic methods. This represents the first reported apoenzyme structure for any E1 component from the homodimeric ,2 family. Electron-density features occurring in the region where the cofactor pyrimidine ring would normally be expected to bind are of size, shape and location compatible with water molecules that form a hydrogen-bonded linkage between residues Glu571 and Val192, which normally make conserved interactions with the ThDP cofactor. A histidine side chain that normally forms hydrogen bonds to ThDP is disordered in its absence and partially occupies two sites. Unlike in the reported heterotetrameric branched-chain apo-E1, no disorder/order loop transformations are evident in apo-PDHc E1 relative to the holo-E1 enzyme (PDHc E1,ThDP,Mg2+). Differences in the extent of hydrogen-bonding networks found in the apo-E1 enzyme, the holo-E1 enzyme and in an inhibitor complex with bound thiamine 2-thiazolone diphosphate (ThTDP), PDHc E1,ThTDP,Mg2+, are described. [source] A unique lipoylation system in the ArchaeaFEBS JOURNAL, Issue 15 2009Lipoylation in Thermoplasma acidophilum requires two proteins Members of the 2-oxoacid dehydrogenase multienzyme complex family play a key role in the pathways of central metabolism. Post-translational lipoylation of the dihydrolipoyl acyltransferase component of these complexes is essential for their activity, the lipoyllysine moiety performing the transfer of substrates and intermediates between the different active sites within these multienzyme systems. We have previously shown that the thermophilic archaeon, Thermoplasma acidophilum, has a four-gene cluster encoding the components of such a complex, which, when recombinantly expressed in Escherichia coli, can be assembled into an active multienzyme in vitro. Crucially, the E. coli host carries out the required lipoylation of the archaeal dihydrolipoyl acyltransferase component. Because active 2-oxoacid dehydrogenase multienzyme complexes have never been detected in any archaeon, the question arises as to whether Archaea possess a functional lipoylation system. In this study, we report the cloning and heterologous expression of two genes from Tp. acidophilum whose protein products together show significant sequence identity with the single lipoate protein ligase enzyme of bacteria. We demonstrate that both recombinantly expressed Tp. acidophilum proteins are required for lipoylation of the acyltransferase, and that the two proteins associate together to carry out this post-translational modification. From the published DNA sequences, we suggest the presence of functional transcriptional and translational regulatory elements, and furthermore we present preliminary evidence that lipoylation occurs in vivo in Tp. acidophilum. This is the first report of the lipoylation machinery in the Archaea, which is unique in that the catalytic activity is dependent on two separate gene products. Structured digital abstract ,,MINT-7103712: E2lipD (uniprotkb:Q9HIA5), CTD (uniprotkb:Q9HKT2) and LplA (uniprotkb:Q9HKT1) physically interact (MI:0915) by molecular sieving (MI:0071) [source] | ||||||||||