Crystal structure of Arabidopsis cyclophilin38 reveals a previously uncharacterized immunophilin fold and a possible autoinhibitory mechanism.
Cyclophilin38 (CYP38) is one of the highly divergent cyclophilins from Arabidopsis thaliana. Here, we report the crystal structure of the At-CYP38 protein (residues 83 to 437 of 437 amino acids) at 2.39-Å resolution. The structure reveals two distinct domains: an N-terminal helical bundle and a C-terminal cyclophilin β-barrel, connected by an acidic loop. Two N-terminal β-strands become part of the C-terminal cyclophilin β-barrel, thereby making a previously undiscovered domain organization. This study shows that CYP38 does not possess peptidyl-prolyl cis/trans isomerase activity and identifies a possible interaction of CYP38 with the E-loop of chlorophyll protein47 (CP47), a component of photosystem II. The interaction of CYP38 with the E-loop of CP47 is mediated through its cyclophilin domain. The N-terminal helical domain is closely packed together with the putative C-terminal cyclophilin domain and establishes a strong intramolecular interaction, thereby preventing the access of the cyclophilin domain to other proteins. This was further verified by protein-protein interaction assays using the yeast two-hybrid system. Furthermore, the non-Leucine zipper N-terminal helical bundle contains several new elements for protein-protein interaction that may be of functional significance. Together, this study provides the structure of a plant cyclophilin and explains a possible mechanism for autoinhibition of its function through an intramolecular interaction.
Department of Biological Sciences, National University of Singapore, Singapore 117543.
Dileep
D
Vasudevan
Aigen
A
Fu
Sheng
S
Luan
Kunchithapadam
K
Swaminathan
D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D021983:Cyclophilins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000378:metabolism; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; C070970:photosystem II, chlorophyll-binding protein, CP-47; D021983:Cyclophilins; C510628:cyclophilin 38, Arabidopsis