Resolution of Trp near UV CD spectra of calmodulin-domain peptide complexes into the 1La and 1Lb component spectra
✍ Scribed by Andreas Barth; Stephen R. Martin; Peter M. Bayley
- Book ID
- 101240775
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1998
- Tongue
- English
- Weight
- 119 KB
- Volume
- 45
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Near uv CD spectra of Trp residues in proteins frequently show a complex line shape deriving from the overlap of 1 L a and 1 L b electronic transitions. This study presents an original empirical method of resolving these components, based on the near uv CD spectra of well-defined complexes of calmodulin domains with target peptides containing a single Trp residue and derived from the skeletal muscle myosin light chain kinase target sequence. Spectra of 4 complexes were used to obtain the 1 L a and 1 L b component spectra that were then used to analyze further complexes. The broad and featureless 1 L a spectrum is centered at 279 nm, the 1 L b spectrum shows vibrational fine structure with maxima at 274.9, 281.5, and 289.8 nm. The CD spectrum of most complexes could successfully be fitted with one 1 L a and one 1 L b spectrum, the 1 L b spectrum being negative for all complexes but the 1 L a spectrum showing either positive or negative sign. Spectra of some complexes, however, failed to be adequately represented by only one 1 L a and one 1 L b spectrum. Instead, they could be fitted with one 1 L b spectrum and two 1 L a spectra with different sign and position. The method is successful in identifying and quantitating the relative intensities of a two-component system, consistent with a single conformation for tryptophan in a protein, and provides a simple indication of cases where a more complicated explanation is required.