tailieunhanh - Báo cáo khoa học: Chromophore attachment in phycocyanin Functional amino acids of phycocyanobilin – a-phycocyanin lyase and evidence for chromophore binding

Covalent attachment of phycocyanobilin (PCB) to thea-subunit of C-phy-cocyanin, 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 laminosusPCC 7603, form a 1 : 1 com-plex. Lyase-mutants were constructed to probe functional domains. | iFEBS Journal Chromophore attachment in phycocyanin Functional amino acids of phycocyanobilin - a-phycocyanin lyase and evidence for chromophore binding Kai-Hong Zhao1 Dong Wu1 Ling Zhang1 Ming Zhou1 Stephan Bohm2 Claudia Bubenzer2 and Hugo Scheer2 1 College of Life Science and Technology Huazhong University of Science and Technology Hubei China 2 Department Biologie I - Bereich Botanik Universitat Munchen Germany Keywords biliproteins biosynthesis cyanobacteria photosynthesis post-translational modification Correspondence . Zhao College of Life Science and Technology Huazhong University of Science and Technology Wuhan 430074 Hubei China Tel. Fax 86 27 8754 1634 E-mail kaihongzhao@ H. Scheer Department Biologie I - Bereich Botanik Universitat Munchen Menzinger Str. 67 D-80638 Munich Germany Fax 49 89 17861 271 Tel. 49 89 17861 295 E-mail Received 10 November 2005 revised 17 January 2006 accepted 20 January 2006 doi Covalent attachment of phycocyanobilin PCB to the a-subunit of C-phy-cocyanin 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 USA 89 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 Km of CpcE L275D and L276D increased by 61 and 700 kcat Km 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 .