Catalyzes the transport of cholesteryl ester, and phospholipid between phospholipid surfaces (By similarity). Does not catalyze transport of triglycerides (PubMed:17924655). Required for the assembly and secretion of plasma lipoproteins that contain apolipoprotein B (PubMed:17924655, PubMed:14657502). Required for normal expression of klf-3 (PubMed:23639358). Heterodimer; heterodimerizes with protein disulfide isomerase. Expressed in the intestine throughout larval stages and adulthood. RNAi-mediated knockdown suppresses the slow germline development and the delayed egg-production of clk-1 mutants, but does not affect the rate of postembryonic development.