Thermodynamics of target peptide recognition by calmodulin and a calmodulin analogue: implications for the role of the central linker.
The thermodynamics of interaction of two model peptides melittin and mastoparan with bovine brain calmodulin (CAM) and a smaller CAM analogue, a calcium binding protein from Entamoeba histolytica (CaBP) in 10 mM MOPS buffer (pH 7.0) was examined using isothermal titration calorimetry (ITC). These data show that CAM binds to both the peptides and the enthalpy of binding is endothermic for melittin and exothermic for mastoparan at 25 degrees C. CaBP binds to the longer peptide melittin, but does not bind to mastoparan, the binding enthalpy being endothermic in nature. Concurrently, we also observe a larger increase in alpha-helicity upon the binding of melittin to CAM when compared to CaBP. The role of hydrophobic interactions in the binding process has also been examined using 8-anilino-1-naphthalene-sulphonic acid (ANS) binding monitored by ITC. These results have been employed to rationalize the energetic consequences of the binding reaction.
Moorthy
A K
AK
Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India.
Gopal
B
B
Satish
P R
PR
Bhattacharya
S
S
Bhattacharya
A
A
Murthy
M R
MR
Surolia
A
A
D000595:Amino Acid Sequence; D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000031:analogs & derivatives* / Q000378:metabolism*; D002151:Calorimetry; D002942:Circular Dichroism; D004748:Entamoeba histolytica / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D036341:Intercellular Signaling Peptides and Proteins; D008555:Melitten / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins; D017386:Sequence Homology, Amino Acid; D013816:Thermodynamics; D014862:Wasp Venoms / Q000378:metabolism
D000817:Anilino Naphthalenesulfonates; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D011994:Recombinant Proteins; D014862:Wasp Venoms; D008555:Melitten; C027132:1-anilino-8-naphthalenesulfonate; C037500:mastoparan