Posttranslational Modification of Maize Chloroplast Pyruvate Orthophosphate Dikinase Reveals the Precise Regulatory Mechanism of Its Enzymatic Activity      . Issue 2 (7th April 2014)

• Record Type: Journal Article
• Authors: Chen, Yi-Bo; Lu, Tian-Cong; Wang, Hong-Xia; Shen, Jie; Bu, Tian-Tian; Chao, Qing; Gao, Zhi-Fang; Zhu, Xin-Guang; Wang, Yue-Feng; Wang, Bai-Chen
• Is Part Of: Plant physiology. Volume 165:Issue 2(2014)
• Page Start: 534
• Page End: 549
• Publication Date: 2014-04-07
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.113.231993
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Change in light intensity, rather than light/dark transition, regulates the activity of pyruvate orthophosphate dikinase in maize via reversible phosphorylation at Thr-527 . Abstract: In C4 plants, pyruvate orthophosphate dikinase (PPDK) activity is tightly dark/light regulated by reversible phosphorylation of an active-site threonine (Thr) residue; this process is catalyzed by PPDK regulatory protein (PDRP). Phosphorylation and dephosphorylation of PPDK lead to its inactivation and activation, respectively. Here, we show that light intensity rather than the light/dark transition regulates PPDK activity by modulating the reversible phosphorylation at Thr-527 (previously termed Thr-456) of PPDK in maize ( Zea mays ). The amount of PPDK (unphosphorylated) involved in C4 photosynthesis is indeed strictly controlled by light intensity, despite the high levels of PPDK protein that accumulate in mesophyll chloroplasts. In addition, we identified a transit peptide cleavage site, uncovered partial amino-terminal acetylation, and detected phosphorylation at four serine (Ser)/Thr residues, two of which were previously unknown in maize. In vitro experiments indicated that Thr-527 and Ser-528, but not Thr-309 and Ser-506, are targets of PDRP. Modeling suggests that the two hydrogen bonds between the highly conserved residues Ser-528 and glycine-525 are required for PDRP-mediated phosphorylation of the active-site Thr-527 of PPDK. Taken together, our results suggest that the regulation of maize plastid PPDK isoform (C4 PPDK) activity is much more complex than previously reported. These diverse regulatory pathways may work alone or in combination to fine-tune C4 PPDK activity in response to changes in lighting.