Unusual Binding of a Potential Biomarker with Human Serum Albumin

Authors

  • Dipanwita De,

    1. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India), Fax: (+91) 22-2570-3480
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  • Harpreet Kaur,

    1. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India), Fax: (+91) 22-2570-3480
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  • Prof. Anindya Datta

    Corresponding author
    1. Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India), Fax: (+91) 22-2570-3480
    • Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India), Fax: (+91) 22-2570-3480

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Abstract

This study investigates the specific binding of a potential biomarker, [2,2′-bipyridyl]-3,3′-diol (BP(OH)2), with human serum albumin (HSA). The binding of BP(OH)2 at the two primary drug-binding sites on HSA (Sudlow′s sites I and II) is explored by a competitive-binding study and monitored by considering the green-light emission from its diketo tautomer. Warfarin is used as a marker for site I and dansyl-L-proline (DP) as a competitor for site II. Steady-state and time-resolved fluorescence measurements affirm that neither of Sudlow′s sites is the binding locus of BP(OH)2. To gain an idea regarding the probable binding site of BP(OH)2, we perform molecular-docking studies, which reveal a close proximity of the probe to Trp-214 in subdomain IIA of HSA. Confirmation of this contention is achieved by studying the quenching of the fluorescence of Trp-214 in the presence of BP(OH)2. Moreover, static quenching seems to be responsible for the depletion of the fluorescence of Trp-214, as manifested by the invariance of the intrinsic fluorescence lifetime of Trp-214, as a function of the concentration of BP(OH)2. Based on displacement and quenching studies, supported by molecular docking, we propose that BP(OH)2 binds in a cleft that separates subdomains IIIA and IIB, which is in close proximity to Trp-214.

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