Complementation of a phycocyanin-bilin lyase from Synechocystis sp. PCC 6803 with a nucleomorph-encoded open reading frame from the cryptophyte Guillardia theta.
BACKGROUND
Cryptophytes are highly compartmentalized organisms, expressing a secondary minimized eukaryotic genome in the nucleomorph and its surrounding remnant cytoplasm, in addition to the cell nucleus, the mitochondrion and the plastid. Because the members of the nucleomorph-encoded proteome may contribute to essential cellular pathways, elucidating nucleomorph-encoded functions is of utmost interest. Unfortunately, cryptophytes are inaccessible for genetic transformations thus far. Therefore the functions of nucleomorph-encoded proteins must be elucidated indirectly by application of methods in genetically accessible organisms.


RESULTS
Orf222, one of the uncharacterized nucleomorph-specific open reading frames of the cryptophyte Guillardia theta, shows homology to slr1649 of Synechocystis sp. PCC 6803. Recently a further homolog from Synechococcus sp. PCC 7002 was characterized to encode a phycocyanin-beta155-bilin lyase. Here we show by insertion mutagenesis that the Synechocystis sp. PCC 6803 slr1649-encoded protein also acts as a bilin lyase, and additionally contributes to linker attachment and/or stability of phycobilisomes. Finally, our results indicate that the phycocyanin-beta155-bilin lyase of Synechocystis sp. PCC 6803 can be complemented in vivo by the nucleomorph-encoded open reading frame orf222.


CONCLUSIONS
Our data show that the loss of phycocyanin-lyase function causes pleiotropic effects in Synechocystis sp. PCC 6803 and indicate that after separating from a common ancestor protein, the phycoerythrin lyase from Guillardia theta has retained its capacity to couple a bilin group to other phycobiliproteins. This is a further, unexpected example of the universality of phycobiliprotein lyases.
Bolte
Kathrin
K
Philipps-Universität Marburg, Laboratorium für Zellbiologie, Karl-von-Frisch Str,, D-35032 Marburg, Germany. kathrin.bolte@staff.uni-marburg.de
Kawach
Oliver
O
Prechtl
Julia
J
Gruenheit
Nicole
N
Nyalwidhe
Julius
J
Maier
Uwe-G
UG
D019295:Computational Biology; D044785:Cryptophyta / Q000235:genetics*; D004591:Electrophoresis, Polyacrylamide Gel; D005816:Genetic Complementation Test; D008190:Lyases / Q000378:metabolism*; D016366:Open Reading Frames / Q000235:genetics*; D045524:Phycobilisomes / Q000201:enzymology; D010802:Phylogeny; D011499:Protein Processing, Post-Translational; D012689:Sequence Homology, Nucleic Acid; D046939:Synechocystis / Q000201:enzymology*; D014461:Ultracentrifugation
D045524:Phycobilisomes; D008190:Lyases; C075919:phycocyanin alpha-subunit phycocyanobilin lyase