THE HEMOGLOBIN SYSTEM OF THE HAGFISH MYXINE GLUTINOSA - AGGREGATION STATE AND FUNCTIONAL-PROPERTIES

Hemoglobin (Hb) from the hagfish Myxine glutinosa is composed of six m ajor monomeric subunits. Some of these subunits aggregate to dimers at low pH, and to tetramers when deoxygenated and at high protein concen tration. The aggregation is inhibited by the presence of KCI. Oxygen e quilibrium studies show the presence of a small Bohr effect which is s trongly reduced by KCI, indicating that it originates from pH-dependen t aggregation. ATP and DPG cause a similar decrease in the Bohr effect . O-2 affinity is dependent on protein concentration, temperature and presence of CO2. Cooperativity is practically absent. O-2 binding prop erties of the separated aggregating and non-aggregating Hbs purified a t low pH cannot account for the functional properties of the composite hemolysate, suggesting the presence of other subunits interactions. T he results are discussed in relation to literature data for other cycl ostome Hbs and for M. glutinosa Hb, where the presence of three major monomeric Hbs and a possible CO2-dependent aggregation had been report ed.