3qrx
From Proteopedia
Chlamydomonas reinhardtii centrin bound to melittin
Structural highlights
Function[MEL_APIME] Melittin: Main toxin of bee venom with strong hemolytic activity. Forms a pore in the cell membrane by inserting into lipid bilayers in an alpha-helical conformation and has multiple effects, probably, as a result of its interaction with negatively charged phospholipids. It inhibits well known transport pumps such as the Na(+)-K(+)-ATPase and the H(+)-K(+)-ATPase. It increases the permeability of cell membranes to ions, particularly Na(+) and indirectly Ca(2+), because of the Na(+)-Ca(2+)-exchange. It acts synergistically with phospholipase A2.[1] Melittin-S: 1.4-fold less hemolytic and adopts a less organized secondary structure than melittin.[2] Publication Abstract from PubMedCentrin 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. Proteins 2011; (c) 2011 Wiley-Liss, Inc. The structure, molecular dynamics, and energetics of centrin-melittin complex.,Sosa Ldel V, Alfaro E, Santiago J, Narvaez D, Rosado MC, Rodriguez A, Gomez AM, Schreiter ER, Pastrana-Rios B Proteins. 2011 Nov;79(11):3132-43. doi: 10.1002/prot.23142. Epub 2011 Aug, 30. PMID:21989934[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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