Underlying data for characterization of phycocyanobilin (PCB) biosynthesis in Galdieria sulphuraria

This dataset contains data for studies of phycocyanobilin (PCB) synthesis
in the red alga Galdieria sulphuraria. Red algae such as G.
sulphuraria utilize phycobilisomes for light harvesting. The
phycobilisomes of early-branching organisms such as G.
sulphuraria or Cyanidioschyzon merolae contain PCB chromophores
but not phycoerythrobilin (PEB), in contrast to the
phycobilisomes of other red algae. The studies reported in this
dataset examine biosynthesis of PCB in G. sulphuraria and C.
merolae, starting from biliverdin IX-alpha (BV), the last known
common precursor for PCB and PEB. In cyanobacteria, phages,
green algae, and land plants, conversion of BV into PCB or PEB is
carried out by a family of enzymes called ferredoxin-dependent
bilin reductases (FDBRs). The current studies demonstrate that G.
sulphuraria, but not C. merolae, require the action of an
additional isomerase to synthesize PCB.Deposited data include phylogenetic
analyses, data for in vitro characterization of recombinantly expressed
FDBRs from G. sulphuraria and C. merolae, and data for fractionation of G.
sulphuraria extracts and isomerase assays on the resulting enriched
fraction. The phylogenetic analyses demonstrates that G. sulphuraria has
two FDBRs, GsPEBA and GsPEBB, whereas C. merolae has a single FDBR,
CmPCYA. CmPCYA would be expected to convert BV into PCB, whereas GsPEBA
would be expected to convert BV into 15,16-dihydrobiliverdin (15,16-DHBV)
and GsPEBB would then convert 15,16-DHBV into PEB rather than PCB. In
vitro characterization demonstrates that all three FDBRs carry out the
expected reactions, meaning that the G. sulphuraria enzymes produce PEB
but the phycobilisomes contain PCB. This conundrum is resolved by
demonstrating the existence of an isomerase in G. sulphuraria extracts
that can convert PEB into PCB.