The goal of this research is to investigate the role of the slr1098 gene in the cyanobacterium Synechocystis sp. PCC 6803, a gene with similarity to cpcE which encodes a subunit of an enzyme involved in bilin attachment to phycocyanin. This protein is hypothesized to be involved in oligomerization of phycocyanin due to previous results showing the mutant made shorter phycocyanin rods. The recombinant Slr1098 protein was produced and purified from E. coli cells. Binding assays showed interaction between Slr1098 and both apo- and holo-phycocyanin, but not to apo-allophycocyanin. Slr1098 blocked bilin addition at Cys-82 on CpcB by the CpcS/CpcU bilin lyase. Size exclusion chromatography and sucrose density gradient analysis of complexes formed suggest that Slr1098 strongly interacts with all intermediate forms of phycocyanin and may be an important checkpoint in the biosynthesis and oligomerization of this protein, but that by itself, Slr1098 does not increase oligomerization of phycocyanin.