Heat-shock and redox-dependent functional switching of an h-type Arabidopsis thioredoxin from a disulfide reductase to a molecular chaperone.
A large number of thioredoxins (Trxs), small redox proteins, have been identified from all living organisms. However, many of the physiological roles played by these proteins remain to be elucidated. We isolated a high M(r) (HMW) form of h-type Trx from the heat-treated cytosolic extracts of Arabidopsis (Arabidopsis thaliana) suspension cells and designated it as AtTrx-h3. Using bacterially expressed recombinant AtTrx-h3, we find that it forms various protein structures ranging from low and oligomeric protein species to HMW complexes. And the AtTrx-h3 performs dual functions, acting as a disulfide reductase and as a molecular chaperone, which are closely associated with its molecular structures. The disulfide reductase function is observed predominantly in the low M(r) forms, whereas the chaperone function predominates in the HMW complexes. The multimeric structures of AtTrx-h3 are regulated not only by heat shock but also by redox status. Two active cysteine residues in AtTrx-h3 are required for disulfide reductase activity, but not for chaperone function. AtTrx-h3 confers enhanced heat-shock tolerance in Arabidopsis, primarily through its chaperone function.
Park
Soo Kwon
SK
Environmental Biotechnology National Core Research Center, Plant Molecular Biology and Biotechnology Research Center , and Division of Applied Life Science (BK21 program), Korea.
Jung
Young Jun
YJ
Lee
Jung Ro
JR
Lee
Young Mee
YM
Jang
Ho Hee
HH
Lee
Seung Sik
SS
Park
Jin Ho
JH
Kim
Sun Young
SY
Moon
Jeong Chan
JC
Lee
Sun Yong
SY
Chae
Ho Byoung
HB
Shin
Mi Rim
MR
Jung
Ji Hyun
JH
Kim
Min Gab
MG
Kim
Woe Yeon
WY
Yun
Dae-Jin
DJ
Lee
Kyun Oh
KO
Lee
Sang Yeol
SY