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Research has been conducted on the member of the Ca (super)2+ -binding proteins, Mts1. The structure-function relationships of this protein and its Ca (super)2+ -dependent interaction with protein binding targets have been investigated and the details are reported.

Research has been conducted on the free energy transfer mechanism in metabolism. The study of the energy-transfer system is presented.

A study was conducted on the transience that is observed during the regulation of energy transfer in the ATP sulfurylase-GTPase system. The findings indicate that Pi binding directs the system through the coupled mechanism and that the mass ratio of the activated sulfate (APS) reaction can be tuned by adjusting flux through the coupled and uncoupled pathways. Moreover, this coupling mechanism provides an approach for controlling the quantity of chemical potential transferred to the APS reaction.

Results show that the calcium-regulated S100 family of protein member, mts1, regulates myosin IIA assembly by monomer sequestration and cell shape and motility by modulating myosin IIA function. Data indicate that mts 1 affects only to a small extent the half-time for myosin IIA assembly while mainly affecting its polymerization.

Phosphorylation on Ser 19 of the myosin II regulatory light chain by myosin light chain kinase (MLCK) regulates actomyosin contractility in smooth muscle and vertebrate nonmuscle cells. The smooth/ nonmuscle MLCK gene locus produces two kinases, a high molecular weight isoform (long MLCK) and a low molecular weight isoform (short MLCK), that are differentially expressed in smooth and nonmuscle tissues. To study the relative localization of the MLCK isoforms in cultured nonmuscle cells and to determine the spatial and temporal dynamics of MLCK localization during mitosis, we constructed green fluorescent protein fusions of the long and short MLCKs. In interphase cells, localization of the long MLCK to stress fibers is mediated by five DXRXXL motifs, which span the junction of the [NH.sub.2]-terminal extension and the short MLCK. In contrast, localization of the long MLCK to the cleavage furrow in dividing cells requires the five DXRXXL motifs as well as additional amino acid sequences present in the [NH.sub.2]-terminal extension. Thus, it appears that nonmuscle cells utilize different mechanisms for targeting the long MLCK to actomyosin structures during interphase and mitosis. Further studies have shown that the long MLCK has twofold lower kinase activity in early mitosis than in interphase or in the early stages of postmitotic spreading. These findings suggest a model in which MLCK and the myosin II phosphatase (Totsukawa, G., Y. Yamakita, S. Yamashiro, H. Hosoya, D.J. Hartshorne, and F. Matsumura. 1999. J. Cell Biol. 144:735-744) act cooperatively to regulate the level of Ser 19-phosphorylated myosin II during mitosis and initiate cytokinesis through the activation of myosin II motor activity. Key words: myosin * phosphorylation * myosin light chain kinase * cell division * cytokinesis