Conservation and Diversity in the Primary Reverse Photodynamics of the Canonical Red/Green Cyanobacteriochrome Family

Biochemistry. 2020 Oct 20;59(41):4015-4028. doi: 10.1021/acs.biochem.0c00454. Epub 2020 Oct 6.

Abstract

In this report, we compare the femtosecond to nanosecond primary reverse photodynamics (15EPg15ZPr) of eight tetrapyrrole binding photoswitching cyanobacteriochromes in the canonical red/green family from the cyanobacterium Nostoc punctiforme. Three characteristic classes were identified on the basis of the diversity of excited-state and ground-state properties, including the lifetime, photocycle initiation quantum yield, photointermediate stability, spectra, and temporal properties. We observed a correlation between the excited-state lifetime and peak wavelength of the electronic absorption spectrum with higher-energy-absorbing representatives exhibiting both faster excited-state decay times and higher photoisomerization quantum yields. The latter was attributed to both an increased number of structural restraints and differences in H-bonding networks that facilitate photoisomerization. All three classes exhibited primary Lumi-Go intermediates, with class II and III representatives evolving to a secondary Meta-G photointermediate. Class II Meta-GR intermediates were orange absorbing, whereas class III Meta-G had structurally relaxed, red-absorbing chromophores that resemble their dark-adapted 15ZPr states. Differences in the reverse and forward reaction mechanisms are discussed within the context of structural constraints.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Bacterial Proteins / metabolism*
  • Kinetics
  • Nostoc / metabolism*
  • Photochemical Processes
  • Photoreceptors, Microbial / metabolism

Substances

  • Bacterial Proteins
  • Photoreceptors, Microbial