VIBRATIONAL CIRCULAR-DICHROISM STUDIES OF EPIDERMAL GROWTH-FACTOR AND BASIC FIBROBLAST GROWTH-FACTOR

Vibrational circular dichroism (VCD) studies are reported for two unrelated recombinant growth factor proteins: epidermal growth factor and basic fibroblast growth factor (bFGF). NMR, electronic CD, and bFGF X-ray studies indicate that these two proteins are primarily composed of β-sheet and loop secondary structure elements with no detectable α-helices. Two reports on solution conformation of these proteins using FTIR absorption spectroscopy with subsequent resolution enhancement confirmed the presence of a large fraction of a β-sheet conformation but in addition indicated the presence of large absorption bands in the 1650-1656 cm-1 region, which are typically assigned to α-helices. The VCD spectra of both proteins have band shapes that strongly resemble those of other high β-sheet fraction proteins, such as the trypsin family of proteins. Quantitative analysis of the VCD spectra also indicates that these proteins are predominantly in β-sheet and extended ("other") conformations with very little α-helix fraction. These results agree with the CD interpretation and affirm that the FTIR peaks in the region 1650-1656 cm-1 can be assigned to loops. This study provides an example of the limitations of using FTIR frequencies alone for examination of protein secondary structure. © 1992.