title: Lipid binding specificity of bovine α-lactalbumin: a multidimensional approach.
abstract: Many soluble proteins are known to interact with membranes in partially disordered states, and the mechanism and relevance of such interactions in cellular processes are beginning to be understood. Bovine α-lactalbumin (BLA) represents an excellent prototype for monitoring membrane interaction due to its conformational plasticity. In this work, we comprehensively monitored the interaction of apo-BLA with zwitterionic and negatively charged membranes utilizing a variety of approaches. We show that BLA preferentially binds to negatively charged membranes at acidic pH with higher binding affinity. This is supported by spectral changes observed with a potential-sensitive membrane probe and fluorescence anisotropy measurements of a hydrophobic probe. Our results show that BLA exhibits a molten globule conformation when bound to negatively charged membranes. We further show, using the parallax approach, that BLA penetrates the interior of negatively charged membranes, and tryptophan residues are localized at the membrane interface. Red edge excitation shift (REES) measurements reveal that the immediate environment of tryptophans in membrane-bound BLA is restricted, and the restriction is dependent on membrane lipid composition. We envision that understanding the mechanism of BLA-membrane interaction would help in bioengineering of α-lactalbumin, and to address the mechanism of tumoricidal and antimicrobial activities of BLA-oleic acid complex.
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
authors.forename: Arunima
authors.initials: A
authors.lastname: Chaudhuri
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India. Electronic address: amit@ccmb.res.in.
authors.forename: Amitabha
authors.initials: A
authors.lastname: Chattopadhyay
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D002942:Circular Dichroism; D005454:Fluorescence Polarization; D007768:Lactalbumin / Q000737:chemistry / Q000378:metabolism*; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D019301:Oleic Acid / Q000378:metabolism*; D011487:Protein Conformation; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D001059:Apoproteins; D008051:Lipid Bilayers; C041966:apo-alpha-lactalbumin; D019301:Oleic Acid; D014364:Tryptophan; D007768:Lactalbumin
keywords: BLA tryptophan; Bovine α-lactalbumin; Di-8-ANEPPS; Lipid–protein interaction; Membrane penetration depth; REES