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The small bilobal calcium regulatory protein calmodulin (CaM) activates numerous target enzymes in response to transient changes in intracellular calcium concentrations. Binding of calcium to the two helix-loop-helix calcium-binding motifs in each of the globular domains induces conformational changes that expose a methionine-rich hydrophobic patch on the(More)
The intracellular calcium ion is one of the most important secondary messengers in eukaryotic cells. Ca(2+) signals are translated into physiological responses by EF-hand calcium-binding proteins such as calmodulin (CaM). Multiple CaM isoforms occur in plant cells, whereas only a single CaM protein is found in animals. Soybean CaM isoform 1 (sCaM1) shares(More)
Calcium- and integrin-binding protein (CIB) is a novel member of the helix-loop-helix family of regulatory calcium-binding proteins which likely has a specific function in hemostasis through its interaction with platelet integrin alphaIIbbeta(3). The significant amino acid sequence homology between CIB and other regulatory calcium-binding proteins such as(More)
Calcium- and integrin-binding protein 1 (CIB1) regulates platelet aggregation in hemostasis through a specific interaction with the alphaIIb cytoplasmic domain of platelet integrin alphaIIbbeta3. In this work we report the structural characteristics of CIB1 in solution and the mechanistic details of its interaction with a synthetic peptide derived from the(More)
The calcium- and integrin-binding protein 1 (CIB1) is a ubiquitous Ca(2+)-binding protein and a specific binding partner for the platelet integrin αIIb cytoplasmic domain, which confers the key role of CIB1 in hemostasis. CIB1 is also known to be involved in apoptosis, embryogenesis, and the DNA damage response. In this study, the solution structures of(More)
The discovery that plants contain multiple calmodulin (CaM) isoforms having variable sequence identity to mammalian CaM has sparked a flurry of new questions regarding the intracellular role of Ca(2+) regulation in plants. To date, the majority of research in this field has focused on the differential enzymatic regulation of various mammalian CaM-dependent(More)
Recent X-ray crystal structures and solution NMR spectroscopy data for calcium- and integrin-binding protein 1 (CIB1) have all revealed a common EF-hand domain structure for the protein. However, the orientation of the two protein domains, the oligomerization state, and the conformations of the N- and C-terminal extensions differ among the structures. In(More)
Calcium- and integrin-binding protein 1 (CIB1) is a ubiquitous, multifunctional regulatory protein consisting of four helix-loop-helix EF-hand motifs. Neither EF-I nor EF-II binds divalent metal ions; however, EF-III is a mixed Mg2+/Ca2+-binding site, and EF-IV is a higher-affinity Ca2+-specific site. Through the generation of several CIB1 mutant proteins,(More)
Pulsed-field gradient (PFG) diffusion NMR spectroscopy studies were conducted with several helix-loop-helix regulatory Ca(2+)-binding proteins to characterize the conformational changes associated with Ca(2+)-saturation and/or binding targets. The calmodulin (CaM) system was used as a basis for evaluation, with similar hydrodynamic radii (R(h)) obtained for(More)
Calmodulin (CaM) is a versatile Ca(2+)-binding protein that regulates the activity of numerous effector proteins in response to Ca(2+) signals. Several CaM-dependent regulatory mechanisms have been identified, including autoinhibitory domain displacement, sequestration of a ligand-binding site, active site reorganization, and target protein dimerization. We(More)