title: Differential native state ruggedness of the two Ca2+-binding domains in a Ca2+ sensor protein.
abstract: Characterization of near-native excited states of a protein provides insights into various biological functions such as co-operativity, protein-ligand, and protein-protein interactions. In the present study, we investigated the ruggedness of the native state of EhCaBP using nonlinear temperature dependence of backbone amide-proton chemical shifts. EhCaBP is a two-domain EF-hand calcium sensor protein consisting of two EF-hands in each domain and binds four Ca2+ ions. It has been observed that approximately 30% of the residues in the protein access alternative conformations. Theoretical modeling suggested that these low-energy excited states are within 2-3 kcal/mol from the native state. Further, it is interesting to note that the residues accessing alternative conformations are more dominated in the C-terminal domain compared with its N-terminal counterpart suggesting that the former is more rugged in its native state. These distinct characteristics of N- and C-terminal domains of a calcium sensor protein belonging to the super family of calmodulin would have implications for domain dependent Ca2+ signaling pathways.
authors.affiliation: Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India. mohanpmk@tifr.res.in
authors.forename: P M Krishna
authors.initials: PM
authors.lastname: Mohan
authors.forename: Sulakshana
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Kandala V R
authors.initials: KV
authors.lastname: Chary
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D020832:EF Hand Motifs; D004748:Entamoeba histolytica / Q000737:chemistry*; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D002135:Calcium-Binding Proteins; D015800:Protozoan Proteins; D002118:Calcium