title: Distinct Features of Cyanophage-encoded T-type Phycobiliprotein Lyase ΦCpeT: THE ROLE OF AUXILIARY METABOLIC GENES.
abstract: Auxiliary metabolic genes (AMG) are commonly found in the genomes of phages that infect cyanobacteria and increase the fitness of the cyanophage. AMGs are often homologs of host genes, and also typically related to photosynthesis. For example, the ΦcpeTgene in the cyanophage P-HM1 encodes a putative phycobiliprotein lyase related to cyanobacterial T-type lyases, which facilitate attachment of linear tetrapyrrole chromophores to Cys-155 of phycobiliprotein β-subunits, suggesting that ΦCpeT may also help assemble light-harvesting phycobiliproteins during infection. To investigate this possibility, we structurally and biochemically characterized recombinant ΦCpeT. The solved crystal structure of ΦCpeT at 1.8-Å resolution revealed that the protein adopts a similar fold as the cyanobacterial T-type lyase CpcT fromNostocsp. PCC7120 but overall is more compact and smaller. ΦCpeT specifically binds phycoerythrobilin (PEB)in vitroleading to a tight complex that can also be formed inEscherichia coliwhen it is co-expressed with genes encoding PEB biosynthesis (i.e. ho1andpebS). The formed ΦCpeT·PEB complex was very stable as the chromophore was not lost during chromatography and displayed a strong red fluorescence with a fluorescence quantum yield of ΦF= 0.3. This complex was not directly able to transfer PEB to the host phycobiliprotein β-subunit. However, it could assist the host lyase CpeS in its function by providing a pool of readily available PEB, a feature that might be important for fast phycobiliprotein assembly during phage infection.
authors.affiliation: Protein Crystallography Group.
authors.forename: Raphael
authors.initials: R
authors.lastname: Gasper
authors.affiliation: Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum.
authors.forename: Julia
authors.initials: J
authors.lastname: Schwach
authors.affiliation: Department of Biology, Division for Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany.
authors.forename: Jana
authors.initials: J
authors.lastname: Hartmann
authors.affiliation: Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum.
authors.forename: Andrea
authors.initials: A
authors.lastname: Holtkamp
authors.affiliation: Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum.
authors.forename: Jessica
authors.initials: J
authors.lastname: Wiethaus
authors.affiliation: Department of Biology, Division for Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany.
authors.forename: Natascha
authors.initials: N
authors.lastname: Riedel
authors.affiliation: Protein Crystallography Group.
authors.forename: Eckhard
authors.initials: E
authors.lastname: Hofmann
authors.affiliation: Physiology of Microorganisms Group, Faculty for Biology and Biotechnology, Ruhr University Bochum, 44780 Bochum; Department of Biology, Division for Microbiology, Technical University Kaiserslautern, 67663 Kaiserslautern, Germany. Electronic address: nfranken@bio.uni-kl.de.
authors.forename: Nicole
authors.initials: N
authors.lastname: Frankenberg-Dinkel
mesh_terms: D001435:Bacteriophages / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D008190:Lyases / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D046937:Nostoc / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism; D052980:Phycobilins / Q000378:metabolism; D052979:Phycobiliproteins / Q000737:chemistry* / Q000378:metabolism; D010799:Phycoerythrin / Q000378:metabolism; D048929:Prochlorococcus / Q000821:virology; D011487:Protein Conformation; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D052980:Phycobilins; D052979:Phycobiliproteins; D014764:Viral Proteins; D010799:Phycoerythrin; C011070:phycoerythrobilin; D008190:Lyases
keywords: bacteriophage; microbiology; photosynthetic pigment; protein crystallization; viral protein