Structural basis of transport of lysophospholipids by human serum albumin

Abstract

Lysophospholipids play important roles in cellular signal transduction and are implicated in many biological processes, including tumorigenesis, angiogenesis, immunity, atherosclerosis, arteriosclerosis, cancer and neuronal survival. The intracellular transport of lysophospholipids is through FA (fatty acid)-binding protein. Lysophospholipids are also found in the extracellular space. However, the transport mechanism of lysophospholipids in the extracellular space is unknown. HSA (human serum albumin) is the most abundant carrier protein in blood plasma and plays an important role in determining the absorption, distribution, metabolism and excretion of drugs. In the present study, LPE (lysophosphatidylethanolamine) was used as the ligand to analyse the interaction of lysophospholipids with HSA by fluorescence quenching and crystallography. Fluorescence measurement showed that LPE binds to HSA with a Kd (dissociation constant) of 5.6 microM. The presence of FA (myristate) decreases this binding affinity (Kd of 12.9 microM). Moreover, we determined the crystal structure of HSA in complex with both myristate and LPE and showed that LPE binds at Sudlow site I located in subdomain IIA. LPE occupies two of the three subsites in Sudlow site I, with the LPE acyl chain occupying the hydrophobic bottom of Sudlow site I and the polar head group located at Sudlow site I entrance region pointing to the solvent. This orientation of LPE in HSA suggests that HSA is capable of accommodating other lysophospholipids and phospholipids. The study provides structural information on HSA-lysophospholipid interaction and may facilitate our understanding of the transport and distribution of lysophospholipids.

Structural Mechanism of Ring-opening Reaction of Glucose by Human Serum Albumin

“…The rHSA⅐glucose and rHSA⅐fructose complexes were prepared at a molar ratio of 1:15. The final HSA concentrations in the complexes were about 100 mg/ml, similar to previous studies (22)(23)(24). The complex was then crystallized by sitting drop vapor diffusion at room temperature by mixing 1 l of the protein complex with 1 l of the precipitant solution containing 25-30% (w/v) polyethylene glycol 3350 in 50 mM potassium phosphate at pH 7.5.…”

A fluorescent fatty acid probe, DAUDA, selectively displaces two myristates bound in human serum albumin

“…The rHSA-myristate complex was prepared at molar ratio of 1:10 similar to the previous reports. 11,17 The complex was then crystallized by sitting drop vapor diffusion at room temperature by mixing 1 lL of the protein complex with 1ul of reservoir solution containing 28-32% (w/v) polyethylene glycol 3350 in 50 mM potassium phosphate at pH 7.5. Crystals of rHSA-myristate grew spontaneously as clusters of rods after several days.…”

“…FA sites 2, 4, and 5 on HSA were proposed to have the high affinity toward FA. 15 Lysophospholipids, which has only one acyl chain attached to glycyl backbone, were also found to bind to HSA, 16 and such binding was observed in the crystal structure of HSA-lysophosphatidylethanolamine complex, 17 suggesting that HSA is an important modulator of lysophospholipids function.…”

“…We have discovered a proper cryoprotectant (5-10% DMSO) to cryo-cool HSA crystals. 17 11-(Dansylamino) undecanoic acid (DAUDA) is one of fluorescent FA probes, containing 11 carbon acyl chain and a polarity-sensitive dansyl-type fluorophore. 20,21 DAUDA has been used to determine the affinity and localization of compounds with long carbon chains (such as natural FAs, monoacylglycerol, and lysophospholipids) on proteins by monitoring excitation and emission at 345 nm and 543 nm.…”

Development of a mass-spectrometry-based lipidomics platform for the profiling of phospholipids and sphingolipids in brain tissues

“…1, PLs normally consist of two fatty acids of between 16 and 20 carbons esterified to a glycerol backbone, and a phosphorous group that is further linked to a head group [2]. Lysophospholipids (LPLs) are derivatives of PLs that lack one of the acyl chains because of hydrolytic removal [3]. Both PLs and LPLs have been well recognized for their functional roles in cellular signal transduction [4,5].…”