Structure and Calcium Binding Properties of a Neuronal Calcium-Myristoyl Switch Protein, Visinin-Like Protein 3.
Visinin-like protein 3 (VILIP-3) belongs to a family of Ca2+-myristoyl switch proteins that regulate signal transduction in the brain and retina. Here we analyze Ca2+ binding, characterize Ca2+-induced conformational changes, and determine the NMR structure of myristoylated VILIP-3. Three Ca2+ bind cooperatively to VILIP-3 at EF2, EF3 and EF4 (KD = 0.52 μM and Hill slope of 1.8). NMR assignments, mutagenesis and structural analysis indicate that the covalently attached myristoyl group is solvent exposed in Ca2+-bound VILIP-3, whereas Ca2+-free VILIP-3 contains a sequestered myristoyl group that interacts with protein residues (E26, Y64, V68), which are distinct from myristate contacts seen in other Ca2+-myristoyl switch proteins. The myristoyl group in VILIP-3 forms an unusual L-shaped structure that places the C14 methyl group inside a shallow protein groove, in contrast to the much deeper myristoyl binding pockets observed for recoverin, NCS-1 and GCAP1. Thus, the myristoylated VILIP-3 protein structure determined in this study is quite different from those of other known myristoyl switch proteins (recoverin, NCS-1, and GCAP1). We propose that myristoylation serves to fine tune the three-dimensional structures of neuronal calcium sensor proteins as a means of generating functional diversity.
Department of Chemistry, University of California Davis, Davis, CA, United States of America.
Congmin
C
Li
Department of Chemistry, University of California Davis, Davis, CA, United States of America.
Sunghyuk
S
Lim
Department of Neurophysiology, Medical Faculty, Ruhr University Bochum, Bochum, Germany.
Karl H
KH
Braunewell
Department of Chemistry, University of California Davis, Davis, CA, United States of America.
James B
JB
Ames
D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D005136:Eye Proteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D019814:Myristic Acid / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism; D051596:Neurocalcin / Q000737:chemistry* / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D051603:Recoverin / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D002135:Calcium-Binding Proteins; D005136:Eye Proteins; C520235:HPCAL1 protein, human; D009419:Nerve Tissue Proteins; D051596:Neurocalcin; D019814:Myristic Acid; D051603:Recoverin; D002118:Calcium