Is AKR2A an essential molecular chaperone for a class of membrane-bound proteins in plants?
The Arabidopsis ankyrin-repeat containing protein 2A (AKR2A) was shown to be an essential molecular chaperone for the peroxisomal membrane-bound ascorbate peroxidase 3 (APX3), because the biogenesis of APX3 depends on the function of AKR2A in plant cells. AKR2A binds specifically to a sequence in APX3 that is made up of a transmembrane domain followed by a few positively charged amino acid residues; this sequence is named as AKR2A-binding sequence or ABS. Interestingly, a sequence in the chloroplast outer envelope protein 7 (OEP7) shares similar features to ABS and is able to bind specifically to AKR2A, suggesting a possibility that proteins with a sequence similar to ABS could bind to AKR2A and they are all likely ligand proteins of AKR2A. This hypothesis was supported by analyzing 5 additional proteins that contain sequences similar to ABS using the yeast two-hybrid technique. A preliminary survey in the Arabidopsis genome indicates that there are at least 500 genes encoding proteins that contain sequences similar to ABS, which raises interesting questions: are these proteins AKR2A's ligand proteins and does AKR2A play a critical role in the biogenesis of these proteins in plants?
Department of Biological Sciences, Texas Tech University, Lubbock, Texas, USA. hong.zhang@ttu.edu
Hong
H
Zhang
Xiao
X
Li
Yizheng
Y
Zhang
Sundaram
S
Kuppu
Guoxin
G
Shen
D017089:Ankyrin Repeat; D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060387:Ascorbate Peroxidases; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D008565:Membrane Proteins; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D010544:Peroxidases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
C451699:AKR2 protein, Arabidopsis; D029681:Arabidopsis Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D014157:Transcription Factors; D010544:Peroxidases; C555294:APX3 protein, Arabidopsis; D060387:Ascorbate Peroxidases