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Crystallization of the bifunctional proteinase/amylase inhibitor PKI‐3 and of its complex with proteinase K
Author(s) -
Pal Gour P.,
Betzel Christian,
Jany Klaus-Dieter,
Saenger Wolfram
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80308-8
Subject(s) - chemistry , subtilisin , crystallization , crystallography , polyethylene glycol , proteinase k , trypsin , enzyme , biochemistry , organic chemistry
One of the three wheat germ inhibitors of proteinase K is bifunctional and inhibits simultaneously proteinase K (or subtilisin but not enzymes of the trypsin family) and insect α‐amylase. The molecular mass of this inhibitor called PKI‐3 is 21 kDa, and the binding constant for proteinase K is 0.8 nM at pH 8.2, 25°C, in 1:1 molar ratio. PKI‐3 was crystallized by microdialysis against 10–12% polyethylene glycol 6000, 50 mM NaH 2 PO 4 , pH 6.7. The crystals have monoclinic space group P2 1 with a = 42.5, b = 65.3, c = 31.5 Å, β = 110°, and diffract beyond 2.0 Å resolution. The complex proteinase K · PKI‐3 was crystallized by equilibrium vapor diffusion under the same conditions. The crystals are needle‐shaped and still too small for X‐ray analysis. Gel electrophoresis established the composition of the crystals.