Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Heparin binding protein (HBP) is an inactive serine protease homologue with important implications in host defense during infections and inflammations. Two mutants of human HBP, [R23S,F25E]HBP and [G175Q]HBP, have been produced to investigate structure-function relationships of residues in the putative lipid A/lipopolysaccharide (LPS) binding site and BPTI (bovine pancreatic trypsin inhibitor) binding site. The X-ray structures have been determined at 1.9 A resolution for [G175Q]HBP and at 2.5 A resolution for the [R23S,F25E]HBP mutant, and the structures have been fully refined to R-factors of 18.2 % and 20.7 %, respectively. The G175Q mutation does not alter the overall structure of the protein, but the ability to bind BPTI has been eliminated, and the mutant mediates only a limited stimulation of the LPS-induced cytokine release from human monocytes. The lipid A/LPS binding property of [G175Q]HBP is comparable with that of native HBP. The R23S,F25E mutations do not affect the binding of lipid A/LPS and BPTI or the LPS-induced cytokine release from human monocytes. This shows that two diverse ligands, lipid A/LPS and BPTI, do not share binding sites. Previously, there was convincing evidence for the proposed lipid A/LPS binding site of HBP. Unexpectedly, the extensive structural changes introduced by mutation of Arg23 and Phe25 do not affect the binding of lipid A/LPS, indicating that another not yet identified site on HBP is involved in the binding of lipid A/LPS.
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PMID:Two mutants of human heparin binding protein (CAP37): toward the understanding of the nature of lipid A/LPS and BPTI binding. 1117 Jan 99