1-N-histidine phosphorylation of ChlD by the AAA⁺ ChlI2 stimulates magnesium chelatase activity in chlorophyll synthesis

Artur Sawicki, Zhou Shuaixiang, Kathrin Kwiatkowski, Meizhong Luo, Robert Willows

    Research output: Contribution to journalArticlepeer-review

    8 Citations (Scopus)

    Abstract

    Magnesium chelatase (Mg-chelatase) inserts magnesium into protoporphyrin during the biosynthesis of chlorophyll and bacteriochlorophyll. Enzyme activity is reconstituted by forming two separate preactivated complexes consisting of a GUN4/ChlH/protoporphyrin IX substrate complex and a ChlI/ChlD enzyme 'motor' complex. Formation of the ChlI/ChlD complex in both Chlamydomonas reinhardtii and Oryza sativa is accompanied by phosphorylation of ChlD by ChlI, but the orthologous protein complex from Rhodobacter capsulatus, BchI/BchD, gives no detectable phosphorylation of BchD. Phosphorylation produces a 1-N-phospho-histidine within ChlD. Proteomic analysis indicates that phosphorylation occurs at a conserved His residue in the C-terminal integrin I domain of ChlD. Comparative analysis of the ChlD phosphorylation with enzyme activities of various ChlI/ChlD complexes correlates the phosphorylation by ChlI2 with stimulation of Mg-chelatase activity. Mutation of the H641 of CrChlD to E641 prevents both phosphorylation and stimulation of Mg-chelatase activity, confirming that phosphorylation at H641 stimulates Mg-chelatase. The properties of ChlI2 compared with ChlI1 of Chlamydomonas and with ChlI of Oryza, shows that ChlI2 has a regulatory role in Chlamydomonas.
    Original languageEnglish
    Pages (from-to)2095-2105
    Number of pages11
    JournalBiochemical Journal
    Volume474
    Issue number12
    DOIs
    Publication statusPublished - Jun 2017

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