6uvb

<table><tr><td colspan='2'>[[6uvb]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Anabaena_cylindrica_PCC_7122 Anabaena cylindrica PCC 7122]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6UVB OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6UVB FirstGlance]. <br>

== Function ==

[https://www.uniprot.org/uniprot/K9ZI18_ANACC K9ZI18_ANACC]

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== Publication Abstract from PubMed ==

Cyanobacteriochromes (CBCRs) are small, linear tetrapyrrole (bilin)-binding photoreceptors in the phytochrome superfamily that regulate diverse light-mediated adaptive processes in cyanobacteria. More spectrally diverse than canonical red/far-red-sensing phytochromes, CBCRs were thought to be restricted to sensing visible and near UV light until recently when several subfamilies with far-red-sensing representatives (frCBCRs) were discovered. Two of these frCBCRs subfamilies have been shown to incorporate bilin precursors with larger pi-conjugated chromophores, while the third frCBCR subfamily uses the same phycocyanobilin precursor found in the bulk of the known CBCRs. To elucidate the molecular basis of far-red light perception by this third frCBCR subfamily, we determined the crystal structure of the far-red-absorbing dark state of one such frCBCR Anacy_2551g3 from Anabaena cylindrica PCC 7122 which exhibits a reversible far-red/orange photocycle. Determined by room temperature serial crystallography and cryocrystallography, the refined 2.7-A structure reveals an unusual all-Z,syn configuration of the phycocyanobilin (PCB) chromophore that is considerably less extended than those of previously characterized red-light sensors in the phytochrome superfamily. Based on structural and spectroscopic comparisons with other bilin-binding proteins together with site-directed mutagenesis data, our studies reveal protein-chromophore interactions that are critical for the atypical bathochromic shift. Based on these analyses, we propose that far-red absorption in Anacy_2551g3 is the result of the additive effect of two distinct red-shift mechanisms involving cationic bilin lactim tautomers stabilized by a constrained all-Z,syn conformation and specific interactions with a highly conserved anionic residue.

Crystal structure of a far-red-sensing cyanobacteriochrome reveals an atypical bilin conformation and spectral tuning mechanism.,Bandara S, Rockwell NC, Zeng X, Ren Z, Wang C, Shin H, Martin SS, Moreno MV, Lagarias JC, Yang X Proc Natl Acad Sci U S A. 2021 Mar 23;118(12). pii: 2025094118. doi:, 10.1073/pnas.2025094118. PMID:33727422<ref>PMID:33727422</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

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== References ==

<references/>

[[Category: Anabaena cylindrica PCC 7122]]