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Full-Text Articles in Medicine and Health Sciences
Circadian Rhythmicity By Autocatalysis, Arun Mehra, Christian I. Hong, Mi Shi, Jennifer J. Loros, Jay C. Dunlap, Peter Ruoff
Circadian Rhythmicity By Autocatalysis, Arun Mehra, Christian I. Hong, Mi Shi, Jennifer J. Loros, Jay C. Dunlap, Peter Ruoff
Dartmouth Scholarship
The temperature compensated in vitro oscillation of cyanobacterial KaiC phosphorylation, the first example of a thermodynamically closed system showing circadian rhythmicity, only involves the three Kai proteins (KaiA, KaiB, and KaiC) and ATP. In this paper, we describe a model in which the KaiA- and KaiB-assisted autocatalytic phosphorylation and dephosphorylation of KaiC are the source for circadian rhythmicity. This model, based upon autocatalysis instead of transcription-translation negative feedback, shows temperature-compensated circadian limit-cycle oscillations with KaiC phosphorylation profiles and has period lengths and rate constant values that are consistent with experimental observations.
Structural And Function Analyses Of The Global Regulatory Protein Sara From Staphylococcus Aureus, Yingfang Liu, Adhar C. Manna, Cheol-Ho Pan, Irina A. Kriksunov
Structural And Function Analyses Of The Global Regulatory Protein Sara From Staphylococcus Aureus, Yingfang Liu, Adhar C. Manna, Cheol-Ho Pan, Irina A. Kriksunov
Dartmouth Scholarship
The sarA locus in Staphylococcus aureus controls the expression of many virulence genes. The sarA regulatory molecule, SarA, is a 14.7-kDa protein (124 residues) that binds to the promoter region of target genes. Here we report the 2.6 Å-resolution x-ray crystal structure of the dimeric winged helix SarA protein, which differs from the published SarA structure dramatically. In the crystal packing, multiple dimers of SarA form a scaffold, possibly via divalent cations. Mutations of individual residues within the DNA-binding helix–turn–helix and the winged region as well as within the metal-binding pocket implicate basic residues R84 and R90 within the winged …