Tris: an allosteric effector of tarantula haemocyanin.
The effect of the chemical buffering component Tris (hydroxy-methyl-amino-methane) and of chloride ions on the oxygen binding of tarantula hemocyanin was studied at constant pH. It revealed that Tris at micromolar concentrations decreases the oxygen pressure at half-saturation (p50) by a factor of more than two, whereas chloride does not influence oxygen affinity. A thermodynamic analysis in terms of the nested model of allostery [(1987) Proc. Natl. Acad. Sci. 84, 1891-1895] indicated that Tris acts a an allosteric activator of oxygen binding by influencing the interaction between the 12-meric half-molecules of the 24-meric tarantula haemocyanin.
Sterner
R
R
Zoologisches Institut der Universität München, Germany.
Bardehle
K
K
Paul
R
R
Decker
H
H
D000494:Allosteric Regulation; D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D006433:Hemocyanins / Q000378:metabolism*; D007700:Kinetics; D009994:Osmolar Concentration; D010100:Oxygen / Q000378:metabolism*; D013112:Spiders / Q000737:chemistry*; D013816:Thermodynamics; D014325:Tromethamine / Q000494:pharmacology*
D002712:Chlorides; D014325:Tromethamine; D006433:Hemocyanins; D010100:Oxygen