1 research outputs found
Structural and Biochemical Characterization of the Bilin Lyase CpcS from Thermosynechococcus elongatus
Cyanobacterial phycobiliproteins
have evolved to capture light
energy over most of the visible spectrum due to their bilin chromophores,
which are linear tetrapyrroles that have been covalently attached
by enzymes called bilin lyases. We report here the crystal structure
of a bilin lyase of the CpcS family from Thermosynechococcus
elongatus (<i>Te</i>CpcS-III). <i>Te</i>CpcS-III is a 10-stranded β barrel with two alpha helices and
belongs to the lipocalin structural family. <i>Te</i>CpcS-III
catalyzes both cognate as well as noncognate bilin attachment to a
variety of phycobiliprotein subunits. <i>Te</i>CpcS-III
ligates phycocyanobilin, phycoerythrobilin, and phytochromobilin to
the alpha and beta subunits of allophycocyanin and to the beta subunit
of phycocyanin at the Cys82-equivalent position in all cases. The
active form of <i>Te</i>CpcS-III is a dimer, which is consistent
with the structure observed in the crystal. With the use of the UnaG
protein and its association with bilirubin as a guide, a model for
the association between the native substrate, phycocyanobilin, and <i>Te</i>CpcS was produced