Chromophore attachment in phycocyanin. Functional amino acids of phycocyanobilin--alpha-phycocyanin lyase and evidence for chromophore binding

The FEBS Journal
Kai-Hong ZhaoHugo Scheer

Abstract

Covalent attachment of phycocyanobilin (PCB) to the alpha-subunit of C-phycocyanin, CpcA, is catalysed by the heterodimeric PCB : CpcA lyase, CpcE/F [Fairchild CD, Zhao J, Zhou J, Colson SE, Bryant DA & Glazer AN (1992) Proc Natl Acad Sci USA89, 7017-7021]. CpcE and CpcF of the cyanobacterium, Mastigocladus laminosus PCC 7603, form a 1 : 1 complex. Lyase-mutants were constructed to probe functional domains. When in CpcE (276 residues) the N terminus was truncated beyond the R33YYAAWWL motif, or the C terminus beyond amino acid 237, the enzyme became inactive. Activity decreases to 20% when C-terminal truncations went beyond L275, which is a key residue: the K(m) of CpcE(L275D) and (L276D) increased by 61% and 700%, k(cat)/K(m) decreased 3- and 83-fold, respectively. The enzyme also lost activity when in CpcF (213 residues) the 20 N-terminal amino acids were truncated; truncation of 53 C-terminal amino acids inhibited complex formation with CpcE, possibly due to misfolding. According to chemical modifications, one accessible arginine and one accessible tryptophan are essential for CpcE activity, and one carboxylate for CpcF. Both subunits bind PCB, as assayed by Ni2+ affinity chromatography, SDS/PAGE and Zn2+-induced fluorescenc...Continue Reading

References

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Dec 29, 2004·Biochimica Et Biophysica Acta·Kai-Hong ZhaoHugo Scheer

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Citations

Oct 4, 2007·Photosynthesis Research·Jun-Ming TuHugo Scheer
Oct 30, 2009·The Journal of Biological Chemistry·Michaela KupkaKai-Hong Zhao
Nov 29, 2017·Proceedings of the National Academy of Sciences of the United States of America·Cheng ZhaoKai-Hong Zhao
Feb 21, 2008·Molecular Microbiology·H Scheer, K-H Zhao
Jul 31, 2014·The Journal of Biological Chemistry·Wei ZhouXiaojing Yang
Mar 20, 2020·Journal of Experimental Botany·Anton Puzorjov, Alistair J McCormick
Sep 15, 2009·Biochemical and Biophysical Research Communications·Melissa J WhitakerBeronda L Montgomery

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