Mutation of yeast Eug1p CXXS active sites to CXXC results in a dramatic increase in protein disulphide isomerase activity
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Standard
Mutation of yeast Eug1p CXXS active sites to CXXC results in a dramatic increase in protein disulphide isomerase activity. / Nørgaard, Per; Winther, Jakob R.
I: Biochemical Journal, Bind 358, Nr. 1, 2001, s. 269-274.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - JOUR
T1 - Mutation of yeast Eug1p CXXS active sites to CXXC results in a dramatic increase in protein disulphide isomerase activity
AU - Nørgaard, Per
AU - Winther, Jakob R.
PY - 2001
Y1 - 2001
N2 - Protein disulphide isomerase (PDI) is an essential protein which is localized to the endoplasmic reticulum of eukaryotic cells. It catalyses the formation and isomerization of disulphide bonds during the folding of secretory proteins. PDI is composed of domains with structural homology to thioredoxin and with CXXC catalytic motifs. EUG1 encodes a yeast protein, Eug1p, that is highly homologous to PDI. However, Eug1p contains CXXS motifs instead of CXXC. In the current model for PDI function both cysteines in this motif are required for PDI-catalysed oxidase activity. To gain more insight into the biochemical properties of this unusual variant of PDI we have purified and characterized the protein. We have furthermore generated a number of mutant forms of Eug1p in which either or both of the active sites have been mutated to a CXXC sequence. To determine the catalytic capacity of the wild-type and mutant forms we assayed activity in oxidative refolding of reduced and denatured procarboxypeptidase Y as well as refolding of bovine pancreatic trypsin inhibitor. The wild-type protein showed very little activity, not only in oxidative refolding but also in assays where only isomerase activity was required. This was surprising, in particular since mutant forms of Eug1p containing a CXXC motif displayed activity close to that of genuine PDI. These results lead us to propose that general disulphide isomerization is not the main function of Eug1p in vivo.
AB - Protein disulphide isomerase (PDI) is an essential protein which is localized to the endoplasmic reticulum of eukaryotic cells. It catalyses the formation and isomerization of disulphide bonds during the folding of secretory proteins. PDI is composed of domains with structural homology to thioredoxin and with CXXC catalytic motifs. EUG1 encodes a yeast protein, Eug1p, that is highly homologous to PDI. However, Eug1p contains CXXS motifs instead of CXXC. In the current model for PDI function both cysteines in this motif are required for PDI-catalysed oxidase activity. To gain more insight into the biochemical properties of this unusual variant of PDI we have purified and characterized the protein. We have furthermore generated a number of mutant forms of Eug1p in which either or both of the active sites have been mutated to a CXXC sequence. To determine the catalytic capacity of the wild-type and mutant forms we assayed activity in oxidative refolding of reduced and denatured procarboxypeptidase Y as well as refolding of bovine pancreatic trypsin inhibitor. The wild-type protein showed very little activity, not only in oxidative refolding but also in assays where only isomerase activity was required. This was surprising, in particular since mutant forms of Eug1p containing a CXXC motif displayed activity close to that of genuine PDI. These results lead us to propose that general disulphide isomerization is not the main function of Eug1p in vivo.
KW - Amino Acid Motifs
KW - Animals
KW - Aprotinin
KW - Binding Sites
KW - Carboxypeptidases
KW - Catalytic Domain
KW - Cathepsin A
KW - Cattle
KW - Disulfides
KW - Escherichia coli
KW - Fungal Proteins
KW - Glutathione
KW - Insulin
KW - Mutation
KW - Oxygen
KW - Plasmids
KW - Protein Disulfide-Isomerases
KW - Protein Folding
KW - Protein Structure, Tertiary
KW - Saccharomyces cerevisiae
KW - Saccharomyces cerevisiae Proteins
KW - Thioredoxins
KW - Time Factors
U2 - 10.1042/bj3580269
DO - 10.1042/bj3580269
M3 - Journal article
C2 - 11485577
VL - 358
SP - 269
EP - 274
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
IS - 1
ER -
ID: 43973768