Hydrophobic Interactions Are the Prevalent Force in Bromelain:Fab´ Complex

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P. Gupta^1,2, M. Saleemuddin^1,3, and R. H. Khan^3*

¹Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India; fax: +91-571-272-1776; E-mail: pawan_g75@hotmail.com

²Current address: Department of Pharmacology, Basic Science Biomedical Engineering, University of Minnesota, 6-120 Jackson hall, 321 Church Street SE, Minneapolis, MN55455, USA

³Interdisciplinary Biotechnology Unit, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India; fax: +91-571-272-1776; E-mail: rizwanhkhan1@yahoo.com; msaleemuddin@rediffmail.com

^* To whom correspondence should be addressed.

Received November 3, 2004; Revision received March 30, 2005

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Antibromelain polyclonal antibodies against stem bromelain were raised in male albino rabbits and the Fab´ monomers isolated from the IgG of the immune sera as reported in our earlier communication (Gupta, P., Khan, R. H., and Saleemuddin, M. (2003) Biochim. Biophys. Acta, 1646, 131-135). Further, as evident from that communication bromelain:Fab´ complex has 1 : 1 stoichiometry. The stability of bromelain:Fab´ complex (1 : 1 stoichiometry) was investigated by far and near-UV CD and fluorescence measurements. Addition of up to 1.8 M NaCl caused no significant changes in fluorescence signals and near-UV CD peak pattern. However, the spectral studies together with gel filtration studies suggest dissociation of the complex beyond 5% (v/v) methanol. These results show that hydrophobic interactions play a pronounced role in the binding of Fab´ to bromelain while electrostatic interactions may be less crucial.

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KEY WORDS: bromelain, Fab´, immunocomplexes, hydrophobic interaction, electrostatic interaction, methanol, NaCl

DOI: 10.1134/S0006297906130050

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