Structure and stability of the potato cysteine protease inhibitor group (cv. Elkana).
The conformational stability of potato cysteine protease inhibitor (PCPI), the second most abundant protease inhibitor group in potato tuber, was investigated at ambient temperature and upon heating using far- and near-UV circular dichroism spectroscopy, fluorescence spectroscopy, and differential scanning calorimetry (DSC). The PCPI isoforms investigated have a highly similar structure at both the secondary and the tertiary level. PCPI isoforms show structural properties similar to those of the potato serine protease inhibitor group and the Kunitz type soybean trypsin inhibitor, a known beta-II protein. Therefore, PCPI isoforms are also classified as members of the beta-II protein subclass. Results show that the thermal unfolding of PCPI isoforms does not follow a two-state mechanism and that at least one intermediate is present. The occurrence of this intermediate is most apparent in the thermal unfolding of PCPI 8.3 as indicated by the presence of two peaks in the DSC thermogram. Additionally, the formation of aggregates (>100 kDa), especially at low scan rates, increases the apparent cooperativity of the unfolding.
Pouvreau
Laurice
L
Department of Agrotechnology and Food Sciences, Laboratory of Food Chemistry, Wageningen University, 6700 EV Wageningen, The Netherlands.
Kroef
Toos
T
Gruppen
Harry
H
van Koningsveld
Gerrit
G
van den Broek
Lambertus A M
LA
Voragen
Alhons G J
AG
D002942:Circular Dichroism; D015853:Cysteine Proteinase Inhibitors / Q000737:chemistry*; D004355:Drug Stability; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D035281:Plant Tubers / Q000737:chemistry*; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry; D011198:Solanum tuberosum / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D015853:Cysteine Proteinase Inhibitors; D020033:Protein Isoforms