Investigate the Existence of Domain Swapped Dimer in iLPB Family

Abstract

Intracellular lipid binding proteins (iLBPs) are responsible for transport of different insoluble hydrophobic molecules in cytosol. Structures of members of this family include ten stranded beta barrel and two alpha helices which are like a cap for binding pocket of these proteins. Recently, we discovered a domain swapped dimer for Human cellular retinol binding protein II (hCRBPII) which is a member of iLBP. In Domain swapping two or more monomers exchange an identical part of their structures and form dimer or higher order oligomers. The swapped region in hCRBPII is three beta strands with two alpha helixes. Existence of domain swapping for this protein may have physiological relevant and may have huge effect on the folding pathway for iLBPs.1 We successfully expressed hCRPBII by Hela Cells and we got closer to find the size of hCRBPII in mammalian expression by using size exclusion chromatography and western blotting technique. The discovery of domain swapping in hCRBPII also led us to research domain swapping in other types of iLBPs, such as human fatty acid binding proteins. We studied domain swapping in fatty acid binding protein 5 (FABP5). FABP5 is responsible for endocannabinoid anandamide (AEA) transport in cytocol.2 We recently found the structure of domain swapped dimer for FABP5 binds to palmitic acid. Our eventual aim is to predict domain swapping from amino acid sequences in iLBPs.