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摘要 : CarH是一种光受体,在Myxococcus xanthus 和 Thermus thermophilus中介导依赖于光的基因调控,以 “维生素B12”衍生物 adenosylcobalamin作为感光细胞色素。

CarH是一种光受体,在Myxococcus xanthus 和 Thermus thermophilus中介导依赖于光的基因调控,以 “维生素B12”衍生物 adenosylcobalamin作为感光细胞色素。Catherine Drennan及同事获得了CarH在三个相关状态下的X-射线晶体结构: 在黑暗中;在自由状态下和与 “operator DNA”相结合状态下;在曝光后。这些结构显示了曝光是怎样触发导致CarH从DNA脱离和导致类胡萝卜素生物合成基因由CarH介导的转录抑制之解除的大构形变化的。


Structural basis for gene regulation by a B12-dependent photoreceptor


Photoreceptor proteins enable organisms to sense and respond to light. The newly discovered CarH-type photoreceptors use a vitamin B12 derivative, adenosylcobalamin, as the light-sensing chromophore to mediate light-dependent gene regulation. Here we present crystal structures ofThermus thermophilus CarH in all three relevant states: in the dark, both free and bound to operator DNA, and after light exposure. These structures provide visualizations of how adenosylcobalamin mediates CarH tetramer formation in the dark, how this tetramer binds to the promoter −35 element to repress transcription, and how light exposure leads to a large-scale conformational change that activates transcription. In addition to the remarkable functional repurposing of adenosylcobalamin from an enzyme cofactor to a light sensor, we find that nature also repurposed two independent protein modules in assembling CarH. These results expand the biological role of vitamin B12 and provide fundamental insight into a new mode of light-dependent gene regulation.

来源: Nature 浏览次数:0


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