The binding of myristoylated N-terminal nonapeptide from neuro-specific protein CAP-23/NAP-22 to calmodulin does not induce the globular structure observed for the calmodulin-nonmyristylated peptide complex.
CAP-23/NAP-22, a neuron-specific protein kinase C substrate, is Nalpha-myristoylated and interacts with calmodulin (CaM) in the presence of Ca2+ ions. Takasaki et al. (1999, J Biol Chem 274:11848-11853) have recently found that the myristoylated N-terminal nonapeptide of CAP-23/NAP-22 (mC/N9) binds to Ca2+ -bound CaM (Ca2+/CaM). In the present study, small-angle X-ray scattering was used to investigate structural changes of Ca2+/CaM induced by its binding to mC/N9 in solution. The binding of one mC/N9 molecule induced an insignificant structural change in Ca2+/CaM. The 1:1 complex appeared to retain the extended conformation much like that of Ca2+/CaM in isolation. However, it could be seen that the binding of two mC/N9 molecules induced a drastic structural change in Ca2+/CaM, followed by a slight structural change by the binding of more than two but less than four mC/N9 molecules. Under the saturated condition (the molar ratio of 1:4), the radius of gyration (Rg) for the Ca2+/CaM-mC/N9 complex was 19.8 +/- 0.3 A. This value was significantly smaller than that of Ca2+/CaM (21.9 +/- 0.3 A), which adopted a dumbbell structure and was conversely 2-3 A larger than those of the complexes of Ca2+/CaM with the nonmyristoylated target peptides of myosin light chain kinase or CaM kinase II, which adopted a compact globular structure. The pair distance distribution function had no shoulder peak at around 40 A, which was mainly due to the dumbbell structure. These results suggest that Ca2+/CaM interacts with Nalpha-myristoylated CAP-23/NAP-22 differently than it does with other nonmyristoylated target proteins. The N-terminal amino acid sequence alignment of CAP-23/NAP-22 and other myristoylated proteins suggests that the protein myristoylation plays important roles not only in the binding of CAP-23/NAP-22 to Ca2+/CaM, but also in the protein-protein interactions related to other myristoylated proteins.
Hayashi
N
N
Division of Biomedical Polymer Science, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Aichi, Japan. nhayashi@fujita-hu.ac.jp
Izumi
Y
Y
Titani
K
K
Matsushima
N
N
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry* / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins; D003598:Cytoskeletal Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D019814:Myristic Acid / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D009474:Neurons / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014961:X-Ray Diffraction / Q000379:methods
D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D003598:Cytoskeletal Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D019814:Myristic Acid; C066853:Basp1 protein, rat; D002118:Calcium