Improved Estimation of the Secondary Structures of Proteins by Vacuum-Ultraviolet Circular Dichroism Spectroscopy

• Published in: Journal of biochemistry (Tokyo) Vol. 138; no. 1; pp. 79 - 88
• Main Authors: Matsuo, Koichi, Yonehara, Ryuta, Gekko, Kunihiko
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.07.2005
• Subjects: circular dichroism; Circular Dichroism - methods; HSA; human serum albumin; lactate dehydrogenase; LDH; Molecular Structure; poly-l-proline type II; PPII; Protein Structure, Secondary; proteins; ribonuclease A; RNase A; secondary-structure analysis; SNase; Software; soybean trypsin inhibitor; Spectrophotometry, Ultraviolet - methods; staphylococcal nuclease; STI; synchrotron radiation; Synchrotrons; vacuum-ultraviolet; vacuum-ultraviolet circular dichroism; VUV; VUVCD; X-Ray Diffraction
• ISSN: 0021-924X; 1756-2651
• DOI: 10.1093/jb/mvi101

The vacuum-ultraviolet circular dichroism (VUVCD) spectra of 16 globular proteins (insulin, lactate dehydrogenase, glucose isomerase, lipase, conalbumin, transferrin, catalase, subtilisin A, [alpha]-amylase, staphylococcal nuclease, papain, thioredoxin, carbonic anhydrase, elastase, avidin, and xylanase) were successfully measured in aqueous solutions at 25°C from 260 to 160 nm under a high vacuum using a synchrotron-radiation VUVCD spectrophotometer. These proteins exhibited characteristic CD spectra below 190 nm that were related to their different secondary structures, which could not be detected with a conventional CD spectrophotometer. The component spectra of [alpha]-helices, {szligbeta}-strands, turns, and unordered structures were obtained by deconvolution analysis of the VUVCD spectra of 31 reference proteins including the 15 proteins reported in our previous paper [Matsuo, K. et al. (2004) J. Biochem. 135, 405-411]. Prediction of the secondary-structure contents using the SELCON3 program was greatly improved, especially for [alpha]-helices, by extending the short-wavelength limit of CD spectra to 160 nm and by increasing the number of reference proteins. The numbers of [alpha]-helix and {szligbeta}-strand segments, which were calculated from the distorted [alpha]-helix and {szligbeta}-strand contents, were close to those obtained on X-ray crystallography. These results demonstrate the usefulness of synchrotron-radiation VUVCD spectroscopy for the secondary structure analysis of proteins.