title: Conformational variability of goat β-lactoglobulin: crystallographic and thermodynamic studies.
abstract: Goat β-lactoglobulin (GLG), lipocalin protein sharing high sequence similarity to bovine β-lactoglobulin (BLG), has been structurally and thermodynamically characterized. Two crystal forms of GLG have been obtained, trigonal (P3121) and orthorhombic (P21212), with unique molecular packing, not observed previously for BLG. In the trigonal structure, GLG molecules have EF-loop in closed conformation while in the orthorhombic structure, for the first time, symmetric and asymmetric dimers of β-lactoglobulin are observed simultaneously. It indicates that the opening or closing EF-loop does not occur in both subunits at the same time but might be sequential and cooperative. Comparison of GLG and BLG structures revealed presence of various conformers of EF and GH. ITC studies showed that at pH 7.5 GLG binds sodium dodecyl sulfate with Gibbs energy similar to BLG, however, with different contribution from enthalpic and entropic component. At pH 7.5 GLG forms dimers with dimerization constant Ka = 34.28 × 10(3) M(-1), significantly higher than observed for BLG. Similar mechanism of conformational changes and ligand binding indicates that GLG and BLG may play analogous biological role.
authors.affiliation: Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Joanna I
authors.initials: JI
authors.lastname: Loch
authors.affiliation: Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Gronostajowa 7, 30-387 Kraków, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Bonarek
authors.affiliation: Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Kraków, Gronostajowa 7, 30-387 Kraków, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Polit
authors.affiliation: Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland; Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Kraków, Poland.
authors.forename: Sylwia
authors.initials: S
authors.lastname: Świątek
authors.affiliation: Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Czub
authors.affiliation: Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland.
authors.forename: Mira
authors.initials: M
authors.lastname: Ludwikowska
authors.affiliation: Department of Crystal Chemistry and Crystal Physics, Faculty of Chemistry, Jagiellonian University in Kraków, Ingardena 3, 30-060 Kraków, Poland. Electronic address: lewinski@chemia.uj.edu.pl.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Lewiński
mesh_terms: D000818:Animals; D002151:Calorimetry; D002417:Cattle; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D006041:Goats / Q000378:metabolism*; D007782:Lactoglobulins / Q000737:chemistry*; D008958:Models, Molecular; D011485:Protein Binding; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D012967:Sodium Dodecyl Sulfate; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D007782:Lactoglobulins; D012967:Sodium Dodecyl Sulfate
keywords: Asymmetric dimer; Goat milk; β-lactoglobulin