Conservation of Dark Recovery Kinetic Parameters and
Structural Features in the Pseudomonadaceae “Short”
Light, Oxygen, Voltage (LOV) Protein Family: Implications for the
Design of LOV-Based Optogenetic Tools
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Abstract
In bacteria and fungi, various light,
oxygen, voltage (LOV) sensory
systems that lack a fused effector domain but instead contain only
short N- and C-terminal extensions flanking the LOV core exist. In
the prokaryotic kingdom, this so-called “short” LOV
protein family represents the third largest LOV photoreceptor family.
This observation prompted us to study their distribution and phylogeny
as well as their photochemical and structural properties in more detail.
We recently described the slow and fast reverting “short”
LOV proteins PpSB1-LOV and PpSB2-LOV from <i>Pseudomonas putida</i> KT2440 whose adduct state lifetimes varied by 3 orders of magnitude
[Jentzsch, K., Wirtz, A., Circolone, F., Drepper, T., Losi, A., Gärtner,
W., Jaeger, K. E., and Krauss, U. (2009) <i>Biochemistry 48</i>, 10321–10333]. We now present evidence of the conservation
of similar fast and slow-reverting “short” LOV proteins
in different <i>Pseudomonas</i> species. Truncation studies
conducted with PpSB1-LOV and PpSB2-LOV suggested that the short N-
and C-terminal extensions outside of the LOV core domain are essential
for the structural integrity and folding of the two proteins. While
circular dichroism and solution nuclear magnetic resonance experiments
verify that the two short C-terminal extensions of PpSB1-LOV and PpSB2-LOV
form independently folding helical structures in solution, bioinformatic
analyses imply the formation of coiled coils of the respective structural
elements in the context of the dimeric full-length proteins. Given
their prototypic architecture, conserved in most more complex LOV
photoreceptor systems, “short” LOV proteins could represent
ideally suited building blocks for the design of genetically encoded
photoswitches (i.e., LOV-based optogenetic tools)