. . "19" . "2005-5-10" . "S100B is a dimeric Ca(2+)-binding protein that undergoes a 90 +/- 3 degrees rotation of helix 3 in the typical EF-hand domain (EF2) upon the addition of calcium. The large reorientation of this helix is a prerequisite for the interaction between each subunit of S100B and target proteins such as the tumor suppressor protein, p53. In this study, Tb(3+) was used as a probe to examine how binding of a 22-residue peptide derived from the C-terminal regulatory domain of p53 affects the rate of Ca(2+) ion dissociation. In competition studies with Tb(3+), the dissociation rates of Ca(2+) (k(off)) from the EF2 domains of S100B in the absence and presence of the p53 peptide was determined to be 60 and 7 s(-)(1), respectively. These data are consistent with a previously reported result, which showed that that target peptide binding to S100B enhances its calcium-binding affinity [Rustandi et al. (1998) Biochemistry 37, 1951-1960]. The corresponding Ca(2+) association rate constants for S100B, k(on), for the EF2 domains in the absence and presence of the p53 peptide are 1.1 x 10(6) and 3.5 x 10(5) M(-)(1) s(-)(1), respectively. These two association rate constants are significantly below the diffusion control ( approximately 10(9) M(-)(1) s(-)(1)) and likely involve both Ca(2+) ion association and a Ca(2+)-dependent structural rearrangement, which is slightly different when the target peptide is present. EF-hand calcium-binding mutants of S100B were engineered at the -Z position (EF-hand 1, E31A; EF-hand 2, E72A; both EF-hands, E31A + E72A) and examined to further understand how specific residues contribute to calcium binding in S100B in the absence and presence of the p53 peptide." . . . "eng" . . "IM" . . . . . . . . . . . . "MEDLINE" . "May" . "0006-2960" . . . . . . . . . "Print" . "17" . "44" . "NLM" . "Y" . "7305-14" . "2007-11-14" . . . . . . . . . . . . . . . . . . . . "2005" . "Calcium-binding properties of wild-type and EF-hand mutants of S100B in the presence and absence of a peptide derived from the C-terminal negative regulatory domain of p53." . "Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, 108 North Greene Street, Baltimore, Maryland 21201, USA." . "Journal Article" . "Comparative Study" . "Research Support, N.I.H., Extramural" . "Research Support, Non-U.S. Gov't" . "Research Support, U.S. Gov't, P.H.S." . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .