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Mayuko Okabe

Publications and source records attributed to Mayuko Okabe.

5 recordsLinked to original sources
PubMed2006

Roles of the intramolecular disulfide bridge in MotX and MotY, the specific proteins for sodium-driven motors in Vibrio spp.

The proteins PomA, PomB, MotX, and MotY are essential for the motor function of Na+-driven flagella in Vibrio spp. Both MotY and MotX have the two cysteine residues (one of which is in a conserved tetrapeptide [CQLV]) that are inferred to form an intramolecular disulfide bond. The cysteine mutants of MotY prevented the formation of an intramolecular disulfide bond, which is presumably important for protein stability. Disruption of the disulfide bridge in MotX by site-directed mutagenesis resulted in increased instability, which did not, however, affect the motility of the cells. These lines of evidence suggest that the intramolecular disulfide bonds are involved in the stability of both proteins, but only MotY requires the intramolecular bridge for proper function.

Amino Acid Sequence↗
PubMed2005

Interactions of MotX with MotY and with the PomA/PomB sodium ion channel complex of the Vibrio alginolyticus polar flagellum.

Rotation of the sodium ion-driven polar flagellum of Vibrio alginolyticus requires the inner membrane sodium ion channel complex PomA/PomB and the outer membrane components MotX and MotY. None of the detergents used in this study were able to solubilize MotX when it was expressed alone. However, when co-expressed with MotY, MotX was solubilized by some detergents. The change in the solubility of MotX suggests that MotY interacts with MotX. In agreement with this, a pull-down assay showed the association of MotY with MotX. Solubilized MotX and MotY eluted in the void volume from a gel-filtration column, suggesting that MotX and MotY form a large oligomeric structure(s). In the absence of MotY, MotX affected membrane localization of the PomA/PomB complex and of PomB alone but not of PomA alone, suggesting an interaction between MotX and PomB. We propose that MotX exhibits multiple interactions with the other motor components, first with MotY for its localization to the outer membrane and then with the PomA/PomB complex through PomB for the motor rotation.

Bacterial Outer Membrane Proteins↗
PubMed2003

Divergent evolutions of trinucleotide polymerization revealed by an archaeal CCA-adding enzyme structure.

CCA-adding enzyme [ATP(CTP):tRNA nucleotidyltransferase], a template-independent RNA polymerase, adds the defined 'cytidine-cytidine-adenosine' sequence onto the 3' end of tRNA. The archaeal CCA-adding enzyme (class I) and eubacterial/eukaryotic CCA-adding enzyme (class II) show little amino acid sequence homology, but catalyze the same reaction in a defined fashion. Here, we present the crystal structures of the class I archaeal CCA-adding enzyme from Archaeoglobus fulgidus, and its complexes with CTP and ATP at 2.0, 2.0 and 2.7 A resolutions, respectively. The geometry of the catalytic carboxylates and the relative positions of CTP and ATP to a single catalytic site are well conserved in both classes of CCA-adding enzymes, whereas the overall architectures, except for the catalytic core, of the class I and class II CCA-adding enzymes are fundamentally different. Furthermore, the recognition mechanisms of substrate nucleotides and tRNA molecules are distinct between these two classes, suggesting that the catalytic domains of class I and class II enzymes share a common origin, and distinct substrate recognition domains have been appended to form the two presently divergent classes.

Adenosine Triphosphate↗
PubMed2002

MotX and MotY, specific components of the sodium-driven flagellar motor, colocalize to the outer membrane in Vibrio alginolyticus.

Rotation of the sodium-driven polar flagella of Vibrio alginolyticus requires four motor proteins: PomA, PomB, MotX and MotY. MotX and MotY, which are unique components of the sodium-driven motor of Vibrio, have been believed to be localized in the inner (cytoplasmic) membrane via their N-terminal hydrophobic segments. Here we show that MotX and MotY colocalize to the outer membrane. Both proteins, when expressed together, were detected in the outer membrane fraction separated by sucrose density gradient centrifugation. As mature MotX and MotY proteins do not have N-terminal hydrophobic segments, the N-termini of the primary translation products must have signal sequences that are removed upon translocation across the inner membrane. Moreover, MotX and MotY require each other for efficient localization to the outer membrane. Based on these lines of evidence, we propose that MotX and MotY form a complex in the outer membrane. This is the first case that describes motor proteins function in the outer membrane for flagellar rotation.

Bacterial Outer Membrane Proteins↗