3rty
From Proteopedia
Structure of an Enclosed Dimer Formed by The Drosophila Period Protein
Structural highlights
Function[PER_DROME] Essential for biological clock functions. Determines the period length of circadian and ultradian rhythms; an increase in PER dosage leads to shortened circadian rhythms and a decrease leads to lengthened circadian rhythms. Essential for the circadian rhythmicity of locomotor activity, eclosion behavior, and for the rhythmic component of the male courtship song that originates in the thoracic nervous system. The biological cycle depends on the rhythmic formation and nuclear localization of the TIM-PER complex. Light induces the degradation of TIM, which promotes elimination of PER. Nuclear activity of the heterodimer coordinatively regulates PER and TIM transcription through a negative feedback loop. Behaves as a negative element in circadian transcriptional loop. Does not appear to bind DNA, suggesting indirect transcriptional inhibition. Publication Abstract from PubMedPeriod (PER) is the major transcription inhibitor in metazoan circadian clocks and lies at the center of several feedback loops that regulate gene expression. Dimerization of Drosophila PER influences nuclear translocation, repressor activity, and behavioral rhythms. The structure of a central, 346-residue PER fragment reveals two associated PAS (Per-Arnt-Sim) domains followed by a protruding alpha-helical extension (alphaF). A closed, pseudo-symmetric dimer forms from a cross handshake interaction of the N-terminal PAS domain with alphaF of the opposing subunit. Strikingly, a shift of alphaF against the PAS beta-sheet generates two alternative subunit interfaces in the dimer. Taken together with a previously reported PER structure in which alphaF extends, these data indicate that alphaF unlatches to switch association of PER with itself to its partner Timeless. The variable positions of the alphaF helix provide snapshots of a helix dissociation mechanism that has relevance to other PAS protein systems. Conservation of PER interaction residues among a family of PAS-AB-containing transcription factors suggests that contacts mediating closed PAS-AB dimers serve a general function. Structure of an enclosed dimer formed by the Drosophila period protein.,King HA, Hoelz A, Crane BR, Young MW J Mol Biol. 2011 Oct 28;413(3):561-72. Epub 2011 Sep 3. PMID:21907720[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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