Plant Physiol, October 2002, Vol. 130, pp. 857-864
Expression and Characterization of the Thylakoid Lumen Protease
DegP1 from Arabidopsis1
Yael
Chassin,
Einat
Kapri-Pardes,
Galit
Sinvany,
Tal
Arad, and
Zach
Adam*
Institute of Plant Sciences, The Hebrew University of Jerusalem,
Rehovot 76100, Israel
The Arabidopsis genome contains 14 genes encoding the serine
protease DegP. Products of four of these genes are located in the
chloroplast: three in the thylakoid lumen and one on the stromal side
of the membrane. We expressed the gene encoding DegP1 as a His-tagged
fusion protein in Escherichia coli, purified the protein
by affinity chromatography, and characterized it biochemically. Size-exclusion chromatography suggested that DegP1 eluted from the
column as a mixture of monomers and hexamers. Proteolytic activity was
characterized using 
-casein as a model substrate. DegP1 demonstrated
concentration-dependent activity, a pH optimum of 6.0 and increasing
activity at elevated temperatures. DegP1 was capable of degrading two
lumenal proteins, plastocyanin and OE33, suggesting a role as a
general-purpose protease in the thylakoid lumen. The results of this
work are discussed in the context of the recent elucidation of the
structure of the E. coli homolog and the possible
physiological role of the protease in the chloroplast lumen.
1
This work was supported by The Israel Science
Foundation (grant no. 122/00 to Z.A.).
*
Corresponding author; e-mail zach{at}agri.huji.ac.il; fax
972-8-946-7763.
© 2002 American Society of Plant Physiologists
