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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 β-chains. Characteristic absorption bands for the parallel β-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 β-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 β-segments, the second "mixed" β-segments, with some strands lying antiparallel and others parallel. None of the observed amide I band frequencies assigned to parallel β-chains occurs in the 1650 cm-1 region associated with helical segments. Copyright © 2022. Published by Elsevier Inc.


Heino Susi, D Michael Byler. Reprint of: Fourier Transform Infrared Study of Proteins with Parallel β-Chains. Archives of biochemistry and biophysics. 2022 Sep 15;726:109235

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PMID: 35660301

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