TITLE:
Isolation, Purification and Characterization of Nucleoids from Synechococcus elongatus PCC 7942
AUTHORS:
Ali Azam Talukder, Takao Kondo
KEYWORDS:
Synechococcus elongatus, Sucrose Gradient, Cyanobacterial Nucleoids, Circadian Clock, KaiC Protein
JOURNAL NAME:
Advances in Microbiology,
Vol.4 No.15,
November
24,
2014
ABSTRACT: The genomic DNA of bacteria is highly
compacted in one or a few bodies known as nucleoids. In order to understand the
overall configuration and physiological activities of the cyanobacterial
nucleoid under various growth conditions and the role(s) of each nucleoid
protein in clock function, thylakoid membrane-associated nucleoids from the Synechococcus elongatus (se) PCC 7942 strain were
isolated and purified in presence of spermidine at low salt concentrations by
sucrose density gradient centrifugation. The sedimentation rates, protein/DNA
composition and microscopic appearances as well as variation in structural
components of clock proteins from the isolated nucleoids were compared under
identical conditions. Microscopic appearances of the nucleoids were consistent
with the sedimentation profiles. The nucleoid structure in the wild type was
more tightly compacted than that in the KaiABC mutant strain. Western
immunoblot analyses revealed that the KaiC was associated with the nucleoid
fraction whereas maximum KaiA was localized in the cytosolic fraction,
supposedly in association with the translation machinery.