title: N-terminal myristoylation alters the calcium binding pathways in neuronal calcium sensor-1.
abstract: Neuronal calcium sensor-1 (NCS-1) interacts with many membranes and cytosolic proteins, both in a Ca(2+)-dependent and in a Ca(2+)-independent manner, and its physiological role is governed by its N-terminal myristoylation. To understand the role of myristoylation in altering Ca(2+) response and other basic biophysical properties, we have characterized the Ca(2+) filling pathways in both myristoylated (myr) and non-myristoylated (non-myr) forms of NCS-1. We have observed that Ca(2+) binds simultaneously to all three active EF-hands in non-myr NCS-1, whereas in the case of myr NCS-1, the process is sequential, where the second EF-hand is filled first, followed by the third and fourth EF-hands. In the case of myr NCS-1, the observed sequential Ca(2+) binding process becomes more prominent in the presence of Mg(2+). Besides, the analysis of (15)N-relaxation data reveals that non-myr NCS-1 is more dynamic than myr NCS-1. The overall molecular tumbling correlation time increases by approximately 20% upon myristoylation. Comparing the apo forms of non-myr NCS-1 and myr NCS-1, we found the possibility of existence of some substates, which are structurally closer to the holo form of the protein. There are more such substates in the case of non-myr NCS-1 than in the case of the myr NCS-1, suggesting that the former accesses larger volumes of conformational substates compared with the latter. Further, the study reveals that the possibility of Ca(2+) binding simultaneously to different parts of the protein is more favourable in non-myr NCS-1 than in myr NCS-1.
authors.affiliation: Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai, India.
authors.forename: Kousik
authors.initials: K
authors.lastname: Chandra
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Ramakrishnan
authors.forename: Yogendra
authors.initials: Y
authors.lastname: Sharma
authors.forename: K V R
authors.initials: KV
authors.lastname: Chary
mesh_terms: D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D019814:Myristic Acid / Q000378:metabolism*; D051580:Neuronal Calcium-Sensor Proteins / Q000737:chemistry / Q000378:metabolism*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011789:Quantum Theory
chemical_list: D051580:Neuronal Calcium-Sensor Proteins; D019814:Myristic Acid; D002118:Calcium