title: Tentative assignment of the potato serine protease inhibitor group as beta-II proteins based on their spectroscopic characteristics.
abstract: Potato serine protease inhibitor (PSPI) is the most abundant protease inhibitor group in potato tuber. The investigated PSPI isoforms have a highly similar structure at both the secondary and the tertiary level. From the results described, PSPI is classified as a beta-II protein based on (1) the presence in the near-UV spectra of sharp peaks, indicating a rigid and compact protein; (2) the sharp transition from the native to the unfolded state upon heating (only 6 degrees C) monitored by a circular dichroism signal at 222 nm; and (3) the similarity in secondary structure to soybean trypsin inhibitor, a known beta-II protein, as indicated by a similar far-UV CD spectrum and a similar amide I band in the IR spectrum. The conformation of PSPI was shown also to be stable at ambient temperature in the pH range 4-7.5. Upon lowering the pH to 3.0, some minor changes in the protein core occur, as observed from the increase of the intensity of the phenylalanine peak in the near-UV CD spectrum.
authors.affiliation: Centre for Protein Technology TNO-WU, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
authors.forename: Laurice
authors.initials: L
authors.lastname: Pouvreau
authors.forename: Harry
authors.initials: H
authors.lastname: Gruppen
authors.forename: Gerrit A
authors.initials: GA
authors.lastname: van Koningsveld
authors.forename: Lambertus A M
authors.initials: LA
authors.lastname: van den Broek
authors.forename: Alphons G J
authors.initials: AG
authors.lastname: Voragen
mesh_terms: D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D004355:Drug Stability; D006358:Hot Temperature; D017510:Protein Folding; D017433:Protein Structure, Secondary; D015842:Serine Proteinase Inhibitors / Q000737:chemistry* / Q000145:classification*; D011198:Solanum tuberosum / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D015842:Serine Proteinase Inhibitors