title: CpeS is a lyase specific for attachment of 3Z-PEB to Cys82 of {beta}-phycoerythrin from Prochlorococcus marinus MED4.
abstract: In contrast to the majority of cyanobacteria, the unicellular marine cyanobacterium Prochlorococcus marinus MED4 uses an intrinsic divinyl-chlorophyll-dependent light-harvesting system for photosynthesis. Despite the absence of phycobilisomes, this high-light adapted strain possesses β-phycoerythrin (CpeB), an S-type lyase (CpeS), and enzymes for the biosynthesis of phycoerythrobilin (PEB) and phycocyanobilin. Of all linear tetrapyrroles synthesized by Prochlorococcus including their 3Z- and 3E-isomers, CpeS binds both isomers of PEB and its biosynthetic precursor 15,16-dihydrobiliverdin (DHBV). However, dimerization of CpeS is independent of bilins, which are tightly bound in a complex at a ratio of 1:1. Although bilin binding by CpeS is fast, transfer to CpeB is rather slow. CpeS is able to attach 3E-PEB and 3Z-PEB to dimeric CpeB but not DHBV. CpeS transfer of 3Z-PEB exclusively yields correctly bound βCys(82)-PEB, whereas βCys(82)-DHBV is a side product of 3E-PEB transfer. Spontaneous 3E- and 3Z-PEB addition to CpeB is faulty, and products are in both cases βCys(82)-DHBV and likely a PEB bound at βCys(82) in a non-native configuration. Our data indicate that CpeS is specific for 3Z-PEB transfer to βCys(82) of phycoerythrin and essential for the correct configuration of the attachment product.
authors.affiliation: Department of Physiology of Microorganisms, Faculty of Biology and Biotechnology, Ruhr-University Bochum, Universitaetsstrasse 150, 44780 Bochum, Germany.
authors.forename: Jessica
authors.initials: J
authors.lastname: Wiethaus
authors.forename: Andrea W U
authors.initials: AW
authors.lastname: Busch
authors.forename: Klaus
authors.initials: K
authors.lastname: Kock
authors.forename: Lars I
authors.initials: LI
authors.lastname: Leichert
authors.forename: Christian
authors.initials: C
authors.lastname: Herrmann
authors.forename: Nicole
authors.initials: N
authors.lastname: Frankenberg-Dinkel
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007536:Isomerism; D008190:Lyases / Q000235:genetics / Q000378:metabolism*; D052980:Phycobilins / Q000096:biosynthesis* / Q000737:chemistry; D010799:Phycoerythrin / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D048929:Prochlorococcus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding
chemical_list: D001426:Bacterial Proteins; D052980:Phycobilins; D010799:Phycoerythrin; C011070:phycoerythrobilin; D008190:Lyases