Characterization of recombinant phytochrome from the cyanobacterium Synechocystis
info:eu-repo/classification/ddc/570
0301 basic medicine
570
Sequence Homology, Amino Acid
biology
Protein Conformation
Molecular Sequence Data
Cyanobacteria
Photoreceptors, Microbial
Life sciences
Recombinant Proteins
Molecular Weight
03 medical and health sciences
Bacterial Proteins
Species Specificity
Spectrophotometry
Escherichia coli
ddc:570
Phytochrome
Apoproteins
Protein Kinases
DOI:
10.1073/pnas.94.22.11792
Publication Date:
2002-07-26T14:31:44Z
AUTHORS (6)
ABSTRACT
The complete sequence of the
Synechocystis
chromosome has revealed a phytochrome-like sequence that yielded an authentic phytochrome when overexpressed in
Escherichia coli
. In this paper we describe this recombinant
Synechocystis
phytochrome in more detail. Islands of strong similarity to plant phytochromes were found throughout the cyanobacterial sequence whereas C-terminal homologies identify it as a likely sensory histidine kinase, a family to which plant phytochromes are related. An
≈
300 residue portion that is important for plant phytochrome function is missing from the
Synechocystis
sequence, immediately in front of the putative kinase region. The recombinant apoprotein is soluble and can easily be purified to homogeneity by affinity chromatography. Phycocyanobilin and similar tetrapyrroles are covalently attached within seconds, an autocatalytic process followed by slow conformational changes culminating in red-absorbing phytochrome formation. Spectral absorbance characteristics are remarkably similar to those of plant phytochromes, although the conformation of the chromophore is likely to be more helical in the
Synechocystis
phytochrome. According to size-exclusion chromatography the native recombinant apoproteins and holoproteins elute predominantly as 115- and 170-kDa species, respectively. Both tend to form dimers
in vitro
and aggregate under low salt conditions. Nevertheless, the purity and solubility of the recombinant gene product make it a most attractive model for molecular studies of phytochrome, including x-ray crystallography.
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