Abstract
Cytochrome c553(Cyt c553) function as mobile electron carriers between the two membrane complexes b-6f and photosystem I (PSI) in cyanobacterium.
In PSI complex purified from T. elongatus, the photosynthetic activity measured by oxygen electrode increased ca. 15-fold by Cyt c of bovine heart to compare with DCIP for electron carrier. More increment of PSI activity was expected using T. elongatus Cyt c553. Mass-production system of Cyt c553 using Escherichia coli was constructed to obtain large amount of T. elongatus Cyt c553.
With genetic manipulation, N-terminus putative signal sequence of the Cyt c553 was deleted, and thrombin cleavage residues and six histidine residues were added to the C-terminus of the Cyt c553. The recombinant protein was co-expressed with cytochrome maturation system CcmABCDEFGH in E. coli for heme attachment. Cytochrome c553 protein was mass-expressed in periplasm and purified with Ni2+-affinity column chromatography. Measurement of absorption spectrum indicated heme attachment in purified Cyt c553. The O2 absorption activity was increased by purified Cyt c553 about 10-fold more than by bovine Cyt c in same concentration.
