Characterization of the interaction of lipid A and lipopolysaccharide with human serum albumin: implications for an endotoxin carrier function for albumin

David, SA and Balaram, P and Mathan, VI (1995) Characterization of the interaction of lipid A and lipopolysaccharide with human serum albumin: implications for an endotoxin carrier function for albumin. In: Journal of Endotoxin Research, 20 (2). pp. 99-106.

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Abstract

The interactions of lipid A and lipopolysaccharide (LPS) with human serum albumin (HSA) were examined using fluorescence methods. Lipid A binds HSA with a stoichiometry of 2:1 with dissociation constants of 1.0 µM and 6.0 µM for the high- and low-affinity interactions, respectively. Lipid A displaces HSA-bound dansylsarcosine competitively, but not HSA-bound warfarin, suggesting that domain III-A, and not domain 11-A, is a lipid A binding site. Domain I does not contribute a site for lipid A. Based on these data, and the structural similarity between subdomains III-A and III-B, it is proposed that these two regions of HSA represent the high- and low-affinity sites of interaction of lipid A. Whole LPS also binds HSA, displacing dansylsarcosine, and its lipid A moiety appears to be the interaction site. However, there are differences between LPS and free lipid A. Polymyxin B forms ternary complexes with LPS bound to HSA, suggesting that the regions on LPS recognized by HSA and polymyxin B are different. The observed affinity of lipid A for HSA and mass action effects due to its abundance in the circulation would imply a major LPS carrier function for HSA.

Item Type:	Journal Article
Publication:	Journal of Endotoxin Research
Publisher:	Sage Publications
Additional Information:	Copyright of this article belongs to Sage Publications.
Department/Centre:	Division of Biological Sciences > Molecular Biophysics Unit
Date Deposited:	28 Apr 2010 06:20
Last Modified:	19 Sep 2010 06:00
URI:	http://eprints.iisc.ac.in/id/eprint/27333

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