Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: UNIPROT:P30536 (
PBS
)
9,886
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The Orange
Carotenoid
Protein (OCP) is responsible for photoprotection in many cyanobacteria. Absorption of blue light drives the conversion of the orange, inactive form (OCP
O
) to the red, active form (OCP
R
). Concomitantly, the N-terminal domain (NTD) and the C-terminal domain (CTD) of OCP separate, which ultimately leads to the formation of a quenched OCP
R
-
PBS
complex. The details of the photoactivation of OCP have been intensely researched. Binding site(s) of OCP
R
on the
PBS
core have also been proposed. However, the post-binding events of the OCP
R
-
PBS
complex remain unclear. Here, we demonstrate that
PBS
-bound OCP
R
is not sufficient as a
PBS
excitation energy quencher. Using site-directed mutagenesis, we generated a suite of single point mutations at OCP Leucine 51 (L51) of Synechocystis 6803. Steady-state and time-resolved fluorescence analyses demonstrated that all mutant proteins are unable to quench the
PBS
fluorescence, owing to either failed OCP binding to
PBS
, or, if bound, an OCP-
PBS
quenching state failed to form. The SDS-PAGE and Western blot analysis support that the L51A (Alanine) mutant binds to the
PBS
and therefore belongs to the second category. We hypothesize that upon binding to
PBS
, OCP
R
likely reorganizes and adopts a new conformational state (OCP
3rd
) different than either OCP
O
or OCP
R
to allow energy quenching, depending on the cross-talk between OCP
R
and its
PBS
core-binding counterpart.
...
PMID:Binding of red form of Orange Carotenoid Protein (OCP) to phycobilisome is not sufficient for quenching. 3193 59
