Abstract
Arabidopsis cyclophilin38 (CYP38) is a thylakoid lumen protein critial for PSII assembly and maintenance, and its C-terminal region serves as the target binding domain. We hypothesized that four conserved residues (R290, F294, Q372, and F374) in the C-terminal domain are critical for the structure and function of CYP38. In yeast two-hybrid and protein pull-down assays, CYP38s with single-sited mutations (R290A, F294A, Q372A, or F374A) did not interact with the CP47 E-loop as the wild-type CYP38. In contrast, CYP38 with the R290A/F294A/Q372A/F374A quadruple mutation could bind the CP47 E-loop. Gene transformation analysis showed that the quadruple mutation prevented CYP38 to efficiently complement the mutant phenotype of cyp38. The C-terminal domain half protein with the quadruple mutation, like the wild-type one, could interact with the N-terminal domain or the CP47 E-loop in vitro. The cyp38 plants expressing CYP38 with the quadruple mutation showed a similar BN-PAGE profile as cyp38, but distinct from the wild type. The CYP38 protein with the quadruple mutation associated with the thylakoid membrane less efficiently than the wild-type CYP38. We concluded that these four conserved residues are indispensable as changes of all these residues together resulted in a subtle conformational change of CYP38 and reduced its intramolecular N-C interaction and the ability to associate with the thylakoid membrane, thus impairing its function in chloroplast.
Highlights
FK506 binding proteins (FKBPs) and cyclophilins (CYPs) are cellular receptors for immunosuppressant drugs FK506 and cyclosporine A, respectively (Harding et al, 1989; Siekierka et al, 1989; Standaert et al, 1990)
We proposed that the C-terminal domain of CYP38 of Arabidopsis serves as the target binding domain, and its conserved residues (R290, F294, Q372, and F374) are important for the structure and function
A large number of auxiliary proteins, including thylakoid lumen immunophilins, have been identified as protein factors involved in photosystem II (PSII) assembly and repair (Nixon et al, 2010; Nickelsen and Rengstl, 2013; Lu, 2016)
Summary
FK506 binding proteins (FKBPs) and cyclophilins (CYPs) are cellular receptors for immunosuppressant drugs FK506 and cyclosporine A, respectively (Harding et al, 1989; Siekierka et al, 1989; Standaert et al, 1990). They are collectively referred as immunophilins and share a common feature of peptidyl-prolyl cis/trans isomerase (PPIase) activity in spite of a lack of significant sequence similarity (Romano et al, 2005). Immunophilins in photosynthetic organisms are functionally critical for photosynthesis, as well as for other important processes, including protein folding, development, and stress response (Luan, 1998; Buchanan and Luan, 2005)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
