Photochemical and biochemical characterization of GUN4 reactions with protoporphyrin IX and phycocyanobilin

These data include characterization of the reactions of GUN4 protein with
bound tetrapyrroles, using GUN4 from the model green alga Chlamydomonas.
In almost all oxygenic photosynthetic organisms, GUN4 functions as a
fourth "accessory" subunit of magnesium chelatase (MgCh), the
enzyme carrying out the committed step in chlorophyll biosynthesis. GUN4
is able to bind a wide range of tetrapyrroles, including the
protoporphyrin IX (PPIX) substrate and magnesium protoporphyrin IX
(MgPPIX) product of the MgCh reaction. GUN4 can also bind linear
tetrapyrroles (bilins) such as phycocyanobilin (PCB), and past work has
shown that the GUN4•PCB complex stimulates MgCh activity by an order of
magnitude in vitro and that both GUN4 and bilin are required for
maintenance of the catalytic subunit of MgCh (CHLH1) in vivo. The current
dataset examines the behavior of the GUN4/PCB/PPIX system both in vivo and
in vitro. In vitro measurements used Chlamydomonas GUN4 protein purified
after recombinant expression in Escherichia coli. Four sub-directories
span a range of data types, all presented as tab-delimited text files. In
addition to the overall README for this dataset, detailed information
about the measurements and reported values are included in a README text
file in each directory.