Fourier transform infrared study of proteins with parallel beta-chains.
Deconvolved and second derivative Fourier transform infrared spectra of the proteins flavodoxin and triosephosphate isomerase have been obtained in the 1600 to 1700 cm-1 (amide I) region. To our knowledge these results provide the first experimental infrared data on proteins with parallel beta-chains. Characteristic absorption bands for the parallel beta-segments are observed at 1626-1639 cm-1 (strong) and close to 1675 cm-1 (weak). Previous theoretical studies based on hypothetical models with large, regular beta-sheets had suggested bands close to 1650 and 1666 cm-1. Our new assignments were confirmed by band area measurements, which yield conformational information in good agreement with results from X-ray diffraction data. The spectra were compared with corresponding spectra of concanavalin A and carboxypeptidase A. The first contains only antiparallel beta-segments, the second "mixed" beta-segments, with some strands lying antiparallel and others parallel. None of the observed amide I band frequencies assigned to parallel beta-chains occurs in the 1650 cm-1 region associated with helical segments.
Susi
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Eastern Regional Research Center, United States Department of Agriculture, Philadelphia, Pennsylvania 19118.
Byler
D M
DM
D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D003208:Concanavalin A; D005418:Flavodoxin; D005583:Fourier Analysis; D046911:Macromolecular Substances; D008958:Models, Molecular; D011487:Protein Conformation; D011506:Proteins; D013055:Spectrophotometry, Infrared; D014305:Triose-Phosphate Isomerase
D005418:Flavodoxin; D046911:Macromolecular Substances; D011506:Proteins; D003208:Concanavalin A; D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D014305:Triose-Phosphate Isomerase