Project description:Lysine acetylation in proteins has recently been globally identified in bacteria and eukaryotes. Even though acetylproteins are known to be involved in various cellular processes, its physiological significance has not yet been resolved. Using a proteomics approach in combination with immunoprecipitation, we identified 197 lysine acetylation sites and 4 N-terminal acetylation sites from 128 proteins in Thermus thermophilus HB8, an extremely thermophilic eubacterium. Our analyses revealed that identified acetylproteins are well conserved across all three domains of life and are mainly involved in central metabolism and translation. To further characterize functional significance, we successfully mapped 113 acetylation sites on their 54 authentic and 59 homologous protein structures. The acetylation in the majority of proteins occurs in ordered structures and the sites were situated near the negatively charged glutamic acid residues. In addition, 59 of 103 acetylations were located within considerable distance that can disrupt electrostatic interactions and hydrogen bonding networks on protein surface, demonstrating the physiological significances of the acetylations. Finally, we further summarized 22 critical acetylation sites related to Schiff-base formation, ligand binding, protein-RNA and protein-protein interaction. The structural information of 113 acetylation sites provides new molecular insight into the role of lysine acetylation in the proteins. Data processing, bioinformatics: MS and MS/MS spectral data were processed by DataAnalysis 4.0 software (Bruker Daltonics). The peak lists containing m/z of precursor ions with that of their product ions were generated by the Compound-Auto MS(n) option of the DataAnalysis 4.0 software. Fifty non-deconvoluted peaks over the intensity threshold 150 and charge deconvoluted peaks in each MS/MS spectrum were exported into peak list files. The spectra were searched against our in-house T. thermophilus HB8 database, containing 2,238 protein sequence entries from the complete genome sequence using Mascot search engine (version 2.3; Matrix Science, London, UK). The acetylated peptides were identified using a mass tolerance of ±0.05 Da for precursor and product ions and allowed a maximum of 6 mis-cleavage sites for trypsin. The carbamidomethylation of cysteine was selected as a fixed modification. The oxidation of methionine, deamidation of asparagine and glutamine, acetylation of lysine and acetylation of protein N-terminus were selected as variable modifications. Only peptides in the confidence range of 99% probability (P value < 0.01) in Mascot ion score were assumed to be identified.
Project description:Translation elongation factor P (EF-P) stimulates ribosomal peptidyltransferase activity. EF-P is conserved in bacteria and is essential for cell viability. Eukarya and Archaea have an EF-P homologue, eukaryotic initiation factor 5A (eIF-5A). In the present study, we determined the crystal structure of EF-P from Thermus thermophilus HB8 at a 1.65-A resolution. EF-P consists of three beta-barrel domains (I, II, and III), whereas eIF-5A has only two domains (N and C domains). Domain I of EF-P is topologically the same as the N domain of eIF-5A. On the other hand, EF-P domains II and III share the same topology as that of the eIF-5A C domain, indicating that domains II and III arose by duplication. Intriguingly, the N-terminal half of domain II and the C-terminal half of domain III of EF-P have sequence homologies to the N- and C-terminal halves, respectively, of the eIF-5A C domain. The three domains of EF-P are arranged in an "L" shape, with 65- and 53-A-long arms at an angle of 95 degrees, which is reminiscent of tRNA. Furthermore, most of the EF-P protein surface is negatively charged. Therefore, EF-P mimics the tRNA shape but uses domain topologies different from those of the known tRNA-mimicry translation factors. Domain I of EF-P has a conserved positive charge at its tip, like the eIF-5A N domain.
Project description:TTHA0281 is a hypothetical protein from Thermus thermophilus HB8 that belongs to an uncharacterized protein family, UPF0150, in the Pfam database and to COG1598 in the National Center for Biotechnology Information Database of Clusters of Orthologous Groups. The X-ray crystal structure of the protein was determined by a multiple-wavelength anomalous dispersion technique and was refined at 1.9 A resolution to a final R factor of 18.5%. The TTHA0281 monomer adopts an alpha-beta-beta-beta-alpha fold and forms a homotetramer. Based on the properties and functions of structural homologues of the TTHA0281 monomer, the TTHA0281 protein is speculated to be involved in RNA metabolism, including RNA binding and cleavage.
Project description:Hypoxanthine-guanine phosphoribosyltransferase (HGPRTase), which is a key enzyme in the purine-salvage pathway, catalyzes the synthesis of IMP or GMP from alpha-D-phosphoribosyl-1-pyrophosphate and hypoxanthine or guanine, respectively. Structures of HGPRTase from Thermus thermophilus HB8 in the unliganded form, in complex with IMP and in complex with GMP have been determined at 2.1, 1.9 and 2.2 A resolution, respectively. The overall fold of the IMP complex was similar to that of the unliganded form, but the main-chain and side-chain atoms of the active site moved to accommodate IMP. The overall folds of the IMP and GMP complexes were almost identical to each other. Structural comparison of the T. thermophilus HB8 enzyme with 6-oxopurine PRTases for which structures have been determined showed that these enzymes can be tentatively divided into groups I and II and that the T. thermophilus HB8 enzyme belongs to group I. The group II enzymes are characterized by an N-terminal extension with additional secondary elements and a long loop connecting the second alpha-helix and beta-strand compared with the group I enzymes.
Project description:Ribosomal protein L27 is located near the peptidyltransferase center at the interface of ribosomal subunits, and is important for ribosomal assembly and function. We report the crystal structure of ribosomal protein L27 from Thermus thermophilus HB8, which was determined by the multiwavelength anomalous dispersion method and refined to an R-factor of 19.7% (R(free) = 23.6%) at 2.8 A resolution. The overall fold is an all beta-sheet hybrid. It consists of two sets of four-stranded beta-sheets formed around a well-defined hydrophobic core, with a highly positive charge on the protein surface. The structure of ribosomal protein L27 from T. thermophilus HB8 in the RNA-free form is investigated, and its functional roles in the ribosomal subunit are discussed.
Project description:TT1887 and TT1465 from Thermus thermophilus HB8 are conserved hypothetical proteins, and are annotated as possible lysine decarboxylases in the Pfam database. Here we report the crystal structures of TT1887 and TT1465 at 1.8 A and 2.2 A resolutions, respectively, as determined by the multiwavelength anomalous dispersion (MAD) method. TT1887 is a homotetramer, while TT1465 is a homohexamer in the crystal and in solution. The structures of the TT1887 and TT1465 monomers contain single domains with the Rossmann fold, comprising six alpha helices and seven beta strands, and are quite similar to each other. The major structural differences exist in the N terminus of TT1465, where there are two additional alpha helices. A comparison of the structures revealed the elements that are responsible for the different oligomerization modes. The distributions of the electrostatic potential on the solvent-accessible surfaces suggested putative active sites.
Project description:Fatty-acid degradation is an oxidative process that involves four enzymatic steps and is referred to as the β-oxidation pathway. During this process, long-chain acyl-CoAs are broken down into acetyl-CoA, which enters the mitochondrial tricarboxylic acid (TCA) cycle, resulting in the production of energy in the form of ATP. Enoyl-CoA hydratase (ECH) catalyzes the second step of the β-oxidation pathway by the syn addition of water to the double bond between C2 and C3 of a 2-trans-enoyl-CoA, resulting in the formation of a 3-hydroxyacyl CoA. Here, the crystal structure of ECH from Thermus thermophilus HB8 (TtECH) is reported at 2.85 Å resolution. TtECH forms a hexamer as a dimer of trimers, and wide clefts are uniquely formed between the two trimers. Although the overall structure of TtECH is similar to that of a hexameric ECH from Rattus norvegicus (RnECH), there is a significant shift in the positions of the helices and loops around the active-site region, which includes the replacement of a longer α3 helix with a shorter α-helix and 310-helix in RnECH. Additionally, one of the catalytic residues of RnECH, Glu144 (numbering based on the RnECH enzyme), is replaced by a glycine in TtECH, while the other catalytic residue Glu164, as well as Ala98 and Gly141 that stabilize the enolate intermediate, is conserved. Their putative ligand-binding sites and active-site residue compositions are dissimilar.