2014N121

Gohara Mizuki
1) Structure and selectivity in bestrophin ion channels
Bestrophin is a medically important protein associated with best disease and conditions like vitelliform macular degeneration. In this study, the authors have reported the crystal structure of a bacterial Bestrophin and based on this structural information, they have performed functional and mutational experiments in human and bacterial cells. The paper also throws light on the role of the disease causing mutations.

2) Structural basis for organohalide respiration
Anaerobic organisms use an alternate electron acceptor for respiration. One such class of organisms are the organohalid respiring bacteria which makes use of the reductive halogenase enzymes. In this paper, the authors report the crystal structure of an archetypal dehalogenase from Sulfurospirillum multivorans (in both apo and substrate bound state). The structures reveal that the substrate binding pocket has very little degrees of conformational freedom and hence explains the steric dependant substrate specificity. Also, the structure obtained in complex with the product of the hehalogenation reaction reveals the regioselectivity of the product. Based on this structure, a model is proposed on how a 2 electron and 1 proton transfer is accompanied while the dehalogrnation is carried out.

Nishino Yuuki
1) Members of the human gut microbiota involved in recovery from Vibrio cholerae infection
In this paper, the authors have perfumed a metagenomic analysis (over a period of time) of the bacterial population in the faeces of Bangladeshi adults living in a disease prone area. They found that there was a correlation between species and the faeces during recovery of the infected adults with that of the gut microbiota of healthy Bangladeshi children. It was found that Ruminococcus obeum increases in its relative abundance upon V. cholerae infection of mice. Using mutational studies of the bacterium in mice, the authors try to elucidate the mechanism through which Ruminococcus obeum inhibits V. cholerae invasion.

Yamaguchi Erika
1) Spatial organization of cytokinesis signaling reconstituted in a cell-free system
In this paper, the authors have reconstituted cytokinesis in a cell free system derived from Xenopus eggs. Using this system which enabled large spatial time scale, the authors reveal new mechanisms involved in the signalling during cytokinesis such as transport of the chromosomal passenger complex along microtubules toward the mid zone by using powerful fluorescence imaging. This would have been difficult to study in living cells.

Kojima Seiji
1) Initial bridges between two ribosomal subunits are formed within 9.4 milliseconds, as studied by time-resolved cryo-EM
In a very interesting experiment using a novel microfluidic device in the sample preparation station of cryo-EM, they authors have shown that the process of bridge formation between the two different ribosomal subunits is sequential and not simultaneous. They show that 8 out of the 12 bridges form within 9.4ms of mixing the two subunits whereas the remaining 4 bridges take longer than 43ms to form. This technique could also be applied to study the stepwise events in the functioning and assembly of other macro molecular machines too.

2) LptE binds to and alters the physical state of LPS to catalyze its assembly at the cell surface
In this paper, the authors report the crystal structure of an E.coli outer membrane protein LptE. Based on the structural information, the lipopolysaccharide-binding site was predicted and was confirmed by biochemical experiments. Using the structural and mutational data, the authors propose a model of LptE as a LPS transfer protein which functions by disaggregating LPS during its transport and facilitating its insertion into the outer membrane.

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