Effects of pH, temperature and Ca2+ content on the conformation of alpha-lactalbumin in a medium modelling physiological conditions.
Data obtained by the intrinsic protein fluorescence technique showed that, in addition to Ca2+ and Mg2+ ions, bovine alpha-lactalbumin also binds physiologically significant Na+ and K+ ions, the nucleotides ATP, ADP, UTP, UDP and UDP-galactose. The release of the bound Ca2+ ions from the protein in a medium modelling physiological conditions (containing Mg2+, Na+, K+, ATP and ADP in physiological concentrations) induced a transition of the protein from the native state of the Ca2+-loaded form to a state which is a mixture of native and and thermally changed states of the apo- and metal bound forms. Any variations in temperature result in changes in the populations of these states. This may be associated with some Ca2+ and temperature dependent regulation of the protein function. Variations of pH within the physiological limits had little influence on the conformation of both Ca2+-loaded and Ca2+-free alpha-lactalbumin.
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D007768:Lactalbumin / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation / Q000187:drug effects*; D012964:Sodium / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013696:Temperature; D014531:Uridine Diphosphate Galactose / Q000378:metabolism
D014531:Uridine Diphosphate Galactose; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D007768:Lactalbumin; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium