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Small protein B (SmpB) is required for trans-translation, binding specifically to tmRNA. We show here the solution structure of SmpB from an extremely thermophilic bacterium, Thermus thermophilus HB8, determined by heteronuclear nuclear magnetic resonance methods. The core of the protein consists of an antiparallel β-barrel twisted up from eight β-strands, each end of which is capped with the second or third helix, and the first helix is located beside the barrel. Its C-terminal sequence (20 residues), which is rich in basic residues, shows a poorly structured form, as often seen in isolated ribosomal proteins. The results are discussed in relation to the oligonucleotide binding fold. [Copyright &y& Elsevier]

Investigates the purification and crystallization of RNA polymerase (RNAP) holoenzyme from Thermus thermophilus. Molecular mechanism of RNAP; Structure of RNAP core enzyme; Process for holoenzyme purification of T. thermophilus cells.

Abstract Background: Transfer RNAs from an extreme thermophile, Thermus thermophilus , commonly possess 2′-O-methylguanosine at position 18 (Gm18) in the D-loop. This modification is post-transcriptionally introduced by tRNA (Gm18) methyltransferase. Results: Partial amino acid sequence data were obtained from purified T. thermophilus tRNA (Gm18) methyltransferase by peptide sequencing and mass spectrometry. The sequence data were used to screen the T. thermophilus genome database currently in progress, resulting in the identification of the corresponding gene. Purified recombinant enzyme showed a strict specificity for methylation at the 2′-OH of G18 in tRNA. Sequence alignment with other known or putative methyltransferases elucidates that tRNA (Gm18) methyltransferases have specific conserved region as well as three consensus motifs found in RNA ribose 2′-O-methyltransferases. The enzyme truncated at its N and C termini by limited tryptic digestion still retained binding activity for S-adenosyl-l-homocysteine, but lost the catalytic activity. Conclusion: This is the first report describing the identification of a methyltransferase gene of the trmH family through the analysis of a purified protein. Further, our results indicate that a restricted region(s) in the terminal amino acid residues of T. thermophilus tRNA (Gm18) methyltransferase are responsible for tRNA recognition and a main part of the enzyme is allocated for a catalytic core. [ABSTRACT FROM AUTHOR]

The carboxyl terminus of the CP43 subunit of photosystem II (PSII) in the thermophilic cyanobacterium, Synechococcus elongatus, was genetically tagged with six consecutive histidine residues to create a metal binding site on the PSII supramolecular complex. The histidine-tagging enabled rapid isolation of an intact cyanobacterial PSII core complex from dodecyl maltoside-solubilized thylakoids by a simple one-step Ni2+-affinity column chromatography. The isolated core complex was in a dimeric form with a molecular mass of about 580 kDa, consisting of five major intrinsic membrane proteins (CP47, CP43, D1, D2 and cytochrome b-559), three extrinsic proteins (33 kDa, 12 kDa, and cytochrome c-550), and a few low molecular mass membrane proteins, and evolved oxygen at a rate as high as 3,400 μmol (mg Chl)−1 h−1 at 45°C with ferricyanide as an electron acceptor. The core complex emitted thermoluminescence B2−, B1− and Q-bands arising from S2QB−, S3QB− and S2QB− charge recombinations at respective emission temperatures of 45, 38 and 20°C, all of which were higher by about 15°C as compared with those in mesophilic spinach BBY membranes. These results indicated that the isolated core complex well retained the intact properties of thermoluminescence of thermophilic cyanobacterial cells, the deeper stabilization of PSII charge pairs. The isolated complex was extremely stable in terms of both protein composition and function, exhibiting no release of extrinsic proteins, no proteolytic degradation in any of its subunits, accompanied by only a slight (less than 10%) loss in oxygen evolution, after dark-incubation at 20°C for 8 d. These properties of the thermophilic PSII core complex are highly useful for various types of studies on PSII. [ABSTRACT FROM AUTHOR]