Kinesin motors are mechano-enzymes that hydrolyze ATP to generate force and directional movement along a microtubule. Nucleotide-dependent conformational changes of the head and neck region of kinesin have been shown by cryoelectron microscopy and spectroscopic techniques. Single molecule analysis supports key predictions of the hand-over-hand model for motility of dimeric conventional kinesin, whereas the discovery of a processive one-headed kinesin strongly supports the biased Brownian ratchet model. In this short review, we summarize the present status of research on the mechanism of kinesin motility.
The reaction mechanism of photoactive yellow protein (PYP) has been proposed based on the high-resolution x-ray crystal structure models of the photocycle intermediates. After the analysis, infrared and UV/Visible spectroscopic studies have been carried out on the intermediates in wild-type and mutated PYP. However, the data from the spectroscopic studies are not consistent with the proposed structural models and the reaction mechanism. Here, we describe the conflicts between the crystallographic and spectroscopic studies and discuss the reaction mechanism of PYP in solution.
A model is proposed that an ATPase called EA4 measures time for an active resumption of embryonic development at the end of Bombyx diapause. The timer function of EA4 comprises a built-in mechanism in the EA4 protein structure and it may undergo a series of conformational changes with time. The carbohydrate moiety of EA4 regulates the time measurement through its interaction with a peptide named PIN. PIN forms an equimolar complex with EA4 and presumably inhibits the conformational change of EA4 to hold the timer. Winter cold is a possible external time cue that induces the dissociation of the complex, which in turn results in the timer activation of EA4. We refer to EA4 as a time interval measuring enzyme, TIME.
Hierarchical folding is still an attractive model to describe the mechanism of immediate decrease in chain-entropy of unfolded proteins, and to describe the molecular behavior implied in the funnel model. To provide an insight into this hierarchical folding mechanism, we are advancing the molecular dissection analysis of a single domain protein, protein G. In this review, we introduce our approach and summarize the findings of the structural hierarchy of proteins inside a domain.
Long DNA molecules above the size of several tens kbp undergo marked discrete transition on their higher-order structure. Recent study on single molecular chain observation indicates that the structural transition of DNA induces discrete ON/OFF switching on transcriptional activity. Changes of environmental parameters induce the morphological variation in folded DNA. We propose a hypothesis that appearance of partially unfolded part on chromatin may concern with the promotion of gene expression.