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Research has been conducted on calcium-binding protein calmodulin, important for eukaryotic signal transduction. Results demonstrate the existence of Ca (super)2+ -dependent communication between the domains indicating that spatially distant residues can respond to Ca (super)2+ binding in calmodulin's N-domain.

Research has been conducted on the use of the C-terminal tail in stabilizing the EF-hand protein. Results indicate that the solvent-exposed regions can affect the protein stability.

Results demonstrate that in the wild-type Paramecium melittin binds to the C-domain of the calmodulin in the absence and/or presence of calcium as revealed by analysis of the binding activity in the mutants. Data further show tertiary collapse of calmodulin upon calcium binding to the N-domain of the protein.

Replication protein A (RPA) has been shown to be required for multiple processes in cellular DNA metabolism, but may also be required in the regulation of gene expression and coordination of the cell cycle. The DNA-binding properties of hRPA and scRPA were characterized and it was found that scRPA has significantly different DNA-binding properties from hRPA, having an occluded binding site 30% larger, and a higher affinity for oligothymidine.

The two domains of calmodulin have unique properties and may have different mechanisms in activating targets. The domains are cloned and the calcium binding affinities and the stability of the domains were determined independently. Results reveal that the amino terminal domain binds calcium more avidly and is protected from proteolysis. The isolated amino terminal domain also exhibits higher binding affinity compared to the amino terminal domain of native calmodulin. The implications of these findings are discussed.

Circular dichroism, fluorescein emission and fluorescence spectroscopy are used for studying the interaction between calmodium (CaM) and [Na.sub.V]1.2 (voltage dependent sodium channel type II) at varying calcium concentrations. The studies have shown that IQ motif has led to a selective decrease in the calcium affinity of the C-domain to an extent such that the N-domain has a slightly higher affinity than the C-domain.

Calcium-binding energetic of 11 viable mutants of PCaM identified by their effects on ion-channel regulation and ensuing irregular stimulus-avoidance behavior of Paramecia were studied by observing calcium-dependent decreases in intrinsic Phe fluorescence that indicated the occupancy of sites I and II in the N-domain and increases in intrinsic Tyr IV in the C-domain. The results suggest that while some of these mutations alter calcium-binding directly, others probably alter CaM-channel association or calcium-triggered conformational change in the context of a ternary complex with the affected ion channel.