title: The structure, molecular dynamics, and energetics of centrin-melittin complex.
abstract: Centrin is a calcium binding protein (CaBP) belonging to the EF-hand superfamily. As with other proteins within this family, centrin is a calcium sensor with multiple biological target proteins. We chose to study Chlamydomonas reinhardtii centrin (Crcen) and its interaction with melittin (MLT) as a model for CaBP complexes due to its amphipathic properties. Our goal was to determine the molecular interactions that lead to centrin-MLT complex formation, their relative stability, and the conformational changes associated with the interaction, when compared to the single components. For this, we determined the thermodynamic parameters that define Crcen-MLT complex formation. Two-dimensional infrared (2D IR) correlation spectroscopy were used to study the amide I', I'*, and side chain bands for (13)C-Crcen, MLT, and the (13)C-Crcen-MLT complex. This approach resulted in the determination of MLT's increased helicity, while centrin was stabilized within the complex. Herein we provide the first complete molecular description of centrin-MLT complex formation and the dissociation process. Also, discussed is the first structure of a CaBP-MLT complex by X-ray crystallography, which shows that MLT has a different binding orientation than previously characterized centrin-bound peptides. Finally, all of the experimental results presented herein are consistent with centrin maintaining an extended conformation while interacting with MLT. The molecular implications of these results are: (1) the recognition of hydrophobic contacts as requirements for initial binding, (2) minimum electrostatic interactions within the C-terminal end of the peptide, and (3) van der Waals interactions within MLTs N-terminal end are required for complex formation.
authors: Department of Chemistry, University of Puerto Rico, Mayagüez, Puerto Rico 00681-9019.
authors: Liliana Del Valle
authors: Ldel V
authors: Sosa
authors: Elisa
authors: E
authors: Alfaro
authors: Jorge
authors: J
authors: Santiago
authors: Daniel
authors: D
authors: Narváez
authors: Marie Cely
authors: MC
authors: Rosado
authors: Aslin
authors: A
authors: Rodríguez
authors: Ana María
authors: AM
authors: Gómez
authors: Eric R
authors: ER
authors: Schreiter
authors: Belinda
authors: B
authors: Pastrana-Ríos
mesh_terms: D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D008555:Melitten / Q000737:chemistry* / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D002135:Calcium-Binding Proteins; D008555:Melitten