HIGH-RESOLUTION CRYSTAL-STRUCTURES AND COMPARISONS OF T-STATE DEOXYHEMOGLOBIN AND 2 LIGANDED T-STATE HEMOGLOBINS - T(ALPHA-OXY)HAEMOGLOBIN AND T(MET)HAEMOGLOBIN

The origin of co-operativity in haemoglobin (Hb) resides in the reduced affinity of the T-state. T-state Hb crystals grown from polyethyleneglycol can be liganded without the molecule switching to the R high affinity state. X-ray analysis of T-state α-oxy Hb and T-state met Hb has identified the structural basis for reduced affinity. The nature of the chemical tension at the haem environment is different in the α and β haems. There are small but definite structural changes associated with ligation in the T-state: these prove to be mostly in the same direction as the larger changes that occur in the T → R transition. © 1992.