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Expression of recombinant psoriasis‐associated fatty acid binding protein in Escherichia coli : Gel electrophoretic characterization, analysis of binding properties and comparison with human serum albumin
Author(s) -
Vorum Henrik,
Madsen Peder,
Svendsen Ib,
Celis Julio E.,
Honoré Bent
Publication year - 1998
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.1150191042
Subject(s) - fatty acid binding protein , chemistry , recombinant dna , biochemistry , escherichia coli , human serum albumin , binding protein , fusion protein , fatty acid , affinity chromatography , bovine serum albumin , microbiology and biotechnology , gel electrophoresis , serum albumin , chromatography , biology , enzyme , gene
The psoriasis‐associated fatty acid binding protein (PA‐FABP, also known as FABP5) is a novel keratinocyte protein that is highly up‐regulated in psoriatic plaques (P. Madsen, H. H. Rasmussen, H. Leffers, B. Honoré and J. E. Celis, J. Invest. Dermatol. 1992, 99 , 299–305). Here we have expressed PA‐FABP in Escherichia coli as a fusion protein containing an NH 2 ‐terminal hexa‐His tag followed by a factor Xa cleavage site. The recombinant protein was expressed at a level of about 30% of the soluble proteins and was purified to homogeneity using a simple two‐step protocol consisting of affinity chromatography on Ni 2+ ‐nitrilotriacetic acid agarose followed by gel filtration. The recombinant protein was then digested with factor Xa and characterized by two‐dimensional gel electrophoresis. The ability of PA‐FABP to bind saturated fatty acids ranging from 6 to 16 carbons was determined directly by dialysis and compared to human serum albumin (HSA). The results showed that PA‐FABP binds multiple molecules of the fatty acids hexanoate (C 6:0 ), octanoate (C 8:0 ), decanoate (C 10:0 ) and laurate (C 12:0 ) with a K 1 of about 10 4 m −1 , and myristate (C 14:0 ) with a K 1 of 4.4 × 10 5 m −1 . Palmitate (C 16:0 ) also bound strongly with multiple molecules. Due to the very low solubility of palmitate its affinity to PA‐FABP was measured relatively to HSA and found to be 8.1 times lower. At ligand/protein ratios below 1, all fatty acids bound to PA‐FABP with about one to three orders of magnitude lower affinity than to HSA. The difference in the fatty acid binding properties of the two proteins may reflect differences in their three‐dimensional structures, which in the case of PA‐FABP consists mainly of β‐sheets while HSA contains predominantly α‐helices.