A study of the interactions between residues in the C‐terminal half of calmodulin by one and two‐dimensional NMR methods and computer modelling

Abstract

Assignments of the six sets of aromatic ring protons and four high‐field‐shifted methyl group protons of the C‐terminal fragment of calmodulin, residues 78–148, was achieved by a combination of one and two‐dimensional NMR spectroscopic methods. A full spectral analysis of the aromatic region in terms of chemical shifts and scalar coupling constants was achieved and confirmed by spectral simulation. A three‐dimensional structural model of the C‐terminal fragment was constructed by interactive computer graphics techniques and combined with nuclear Overhauser enhancements to propose sequence assignments for all aromatic and high‐field‐shifted methyl groups. This computer‐generated three‐dimensional model was generally supported by the fact that it qualitatively accounted for many of the ring‐current‐shifted proton resonances and the intraresidue and interresidue nuclear Overhauser enhancements.