Crystal structure of TTHA1657 (AT-rich DNA-binding protein; p25) from Thermus thermophilus HB8 at 2.16 A resolution.
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Base Sequence↗
Biomedical subjects
Hirofumi Komori
Publications and source records attributed to Hirofumi Komori.
Human DNA replication-related element binding factor (hDREF) self-association via hATC domain is necessary for its nuclear accumulation and DNA binding.
We previously demonstrated that hDREF, a human homologue of Drosophila DNA replication-related element binding factor (dDREF), is a DNA-binding protein predominantly distributed with granular structures in the nucleus. Here, glutathione S-transferase pulldown and chemical cross-linking assays showed that the carboxyl-terminal hATC domain of hDREF, highly conserved among hAT transposase family members, possesses self-association activity. Immunoprecipitation analyses demonstrated that hDREF self-associates in vivo, dependent on hATC domain. Moreover, analyses using a series of hDREF mutants carrying amino acid substitutions in the hATC domain revealed that conserved hydrophobic amino acids are essential for self-association. Immunofluorescence studies further showed that all hDREF mutants lacking self-association activity failed to accumulate in the nucleus. Self-association-defective hDREF mutants also lost association with endogenous importin beta1. Moreover, electrophoretic gel-mobility shift assays revealed that the mutations completely abolished the DNA binding activity of hDREF. These results suggest that self-association of hDREF via the hATC domain is necessary for its nuclear accumulation and DNA binding. We also found that ZBED4/KIAA0637, another member of the human hAT family, also self-associates, again dependent on the hATC domain, with deletion resulting in loss of efficient nuclear accumulation. Thus, hATC domains of human hAT family members appear to have conserved functions in self-association that are required for nuclear accumulation.
Active Transport, Cell Nucleus↗
Head module control of mediator interactions.
Yeast Mediator proteins interacting with Med17(Srb4) have been expressed at a high level with the use of recombinant baculoviruses and recovered in homogeneous form as a seven subunit, 223 kDa complex. Electron microscopy and single-particle analysis identify this complex as the Mediator head module. The recombinant head module complements "headless" Mediator for the initiation of transcription in vitro. The module interacts with an RNA polymerase II-TFIIF complex, but not with the polymerase or TFIIF alone. This interaction is lost in the presence of a DNA template and associated RNA transcript, recapitulating the release of Mediator that occurs upon the initiation of transcription. Disruption of the head module in a temperature-sensitive mutant in vivo leads to the release of middle and tail modules from a transcriptionally active promoter. The head module evidently controls Mediator-RNA polymerase II and Mediator-promoter interactions.
Baculoviridae↗
Crystallization and preliminary X-ray analysis of CooA from Carboxydothermus hydrogenoformans.
CooA, a homodimeric haem-containing protein, is responsible for transcriptional regulation in response to carbon monoxide (CO). It has a b-type haem as a CO sensor. Upon binding CO to the haem, CooA binds promoter DNA and activates expression of genes for CO metabolism. CooA from Carboxydothermus hydrogenoformans has been overexpressed in Escherichia coli, purified and crystallized by the vapour-diffusion method. The crystal belongs to space group P2(1), with unit-cell parameters a = 61.8, b = 94.7, c = 92.8 angstroms, beta = 104.8 degrees. The native and anomalous difference Patterson maps indicated that two CooA dimers are contained in the asymmetric unit and are related by a translational symmetry almost parallel to the c axis.
Bacterial Proteins↗
Structure of a conserved hypothetical protein, TTHA0849 from Thermus thermophilus HB8, at 2.4 A resolution: a putative member of the StAR-related lipid-transfer (START) domain superfamily.
The crystal structure of a conserved hypothetical protein, TTHA0849 from Thermus thermophilus HB8, has been determined at 2.4 A resolution as a part of a structural and functional genomics project on T. thermophilus HB8. The main-chain folding shows a compact alpha+beta motif, forming a hydrophobic cavity in the molecule. A structural similarity search reveals that it resembles those steroidogenic acute regulatory proteins that contain the lipid-transfer (START) domain, even though TTHA0849 shows comparatively weak sequence identity to polyketide cyclases. However, the size of the ligand-binding cavity is distinctly smaller than other START domain-containing proteins, suggesting that it catalyses the transfer of smaller ligand molecules.
Crystallography, X-Ray↗
Ubiquitin ligase activity of TFIIH and the transcriptional response to DNA damage.
Core transcription factor (TF) IIH purified from yeast possesses an E3 ubiquitin (Ub) ligase activity, which resides, at least in part, in a RING finger (RNF) domain of the Ssl1 subunit. Yeast strains mutated in the Ssl1 RNF domain are sensitive to ultraviolet (UV) light and to methyl methanesulfonate (MMS). This increased sensitivity to DNA-damaging agents does not reflect a deficiency in nucleotide excision repair. Rather, it correlates with reduced transcriptional induction of genes involved in DNA repair, suggesting that the E3 Ub ligase activity of TFIIH mediates the transcriptional response to DNA damage.
Amino Acid Sequence↗
Activation process of [NiFe] hydrogenase elucidated by high-resolution X-ray analyses: conversion of the ready to the unready state.
Hydrogenases catalyze oxidoreduction of molecular hydrogen and have potential applications for utilizing dihydrogen as an energy source. [NiFe] hydrogenase has two different oxidized states, Ni-A (unready, exhibits a lag phase in reductive activation) and Ni-B (ready). We have succeeded in converting Ni-B to Ni-A with the use of Na2S and O2 and determining the high-resolution crystal structures of both states. Ni-B possesses a monatomic nonprotein bridging ligand at the Ni-Fe active site, whereas Ni-A has a diatomic species. The terminal atom of the bridging species of Ni-A occupies a similar position as C of the exogenous CO in the CO complex (inhibited state). The common features of the enzyme structures at the unready (Ni-A) and inhibited (CO complex) states are proposed. These findings provide useful information on the design of new systems of biomimetic dihydrogen production and fuel cell devices.
Catalytic Domain↗
DNA apophotolyase from Anacystis nidulans: 1.8 A structure, 8-HDF reconstitution and X-ray-induced FAD reduction.
DNA photolyase is a unique flavoenzyme that repairs UV-induced DNA lesions using the energy of visible light. Anacystis nidulans photolyase contains a light-harvesting chromophore, 8-hydroxy-5-deazaflavin (8-HDF), and flavin adenine dinucleotide (FAD) which, in contrast to the 8-HDF chromophore, is indispensable for catalytic activity. This work reports the crystallization and structure at 1.8 A resolution of DNA photolyase devoid of its 8-HDF chromophore (apophotolyase). The overall three-dimensional structure is similar to that of the holoenzyme, indicating that the presence of 8-HDF is not essential for the correct folding of the enzyme. Structural changes include an additional phosphate group, a different conformation for Arg11 and slight rearrangements of Met47, Asp101 and Asp382, which replace part of the 8-HDF molecule in the chromophore-binding pocket. The apophotolyase can be efficiently reconstituted with synthetic 8-hydroxy-5-deazariboflavin, despite the orientation of Arg11 and the presence of the phosphate group in the 8-HDF pocket. Red light or X-rays reduced the FAD chromophore in apophotolyase crystals, as observed by single-crystal spectrophotometry. The structural effects of FAD reduction were determined by comparison of three data sets that were successively collected at 100 K, while the degree of reduction was monitored online by changes in the light absorption of the crystals. X-ray-induced conformational changes were confined to the active site of the protein. They include sub-ångström movements of the O(2) and N(5) atoms of the flavin group as well as the O(delta) atoms of the surrounding amino acids Asp380 and Asn386.
Apoproteins↗
The N-terminal domain of the replication initiator protein RepE is a dimerization domain forming a stable dimer.
The initiator protein RepE of the mini-F plasmid in Escherichia coli plays an essential role in DNA replication, which is regulated by the molecular chaperone-dependent oligomeric state (monomer or dimer). Crosslinking, ultracentrifugation, and gel filtration analyses showed that the solely expressed N-terminal domain (residues 1-144 or 1-152) exists in the dimeric state as in the wild-type RepE protein. This result indicates that the N-terminal domain functions as a dimerization domain of RepE and might be important for the interaction with the molecular chaperones. The N-terminal domain dimer has been crystallized in order to obtain structural insight into the regulation of the monomer/dimer conversion of RepE.
Bacterial Proteins↗
Revised subunit structure of yeast transcription factor IIH (TFIIH) and reconciliation with human TFIIH.
Tfb4 is identified as a subunit of the core complex of yeast RNA polymerase II general transcription factor IIH (TFIIH) by affinity purification, by peptide sequence analysis, and by expression of the entire complex in insect cells. Tfb3, previously identified as a component of the core complex, is shown instead to form a complex with cdk and cyclin subunits of TFIIH. This reassignment of subunits resolves a longstanding discrepancy between yeast and human TFIIH complexes.
Amino Acid Sequence↗