title: PEP-19, an intrinsically disordered regulator of calmodulin signaling.
abstract: PEP-19 is a small calmodulin (CaM)-binding protein that greatly increases the rates of association and dissociation of Ca(2+) from the C-domain of CaM, an effect that is mediated by an acidic/IQ sequence in PEP-19. We show here using NMR that PEP-19 is an intrinsically disordered protein, but with residual structure localized to its acidic/IQ motif. We also show that the k(on) and k(off) rates for binding PEP-19 to apo-CaM are at least 50-fold slower than for binding to Ca(2+)-CaM. These data indicate that intrinsic disorder confers plasticity that allows PEP-19 to bind to either apo- or Ca(2+)-CaM via different structural modes, and that complex formation may be facilitated by conformational selection of residual structure in the acidic/IQ sequence.
authors.affiliation: Department of Biochemistry and Molecular Biology and the Structural Biology Center, University of Texas, Houston Medical School, Houston, Texas 77030, USA.
authors.forename: Quinn K
authors.initials: QK
authors.lastname: Kleerekoper
authors.forename: John A
authors.initials: JA
authors.lastname: Putkey
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D002147:Calmodulin; D009419:Nerve Tissue Proteins; C050394:PCP4 protein, human; D002118:Calcium