[Lupine leghemoglobin affinity to ligands. The effect of pH and buffer nature]. / Izuchenie srodstva leggemoglibina liupina k ligandam. Bliianie rN i prirody bufera.

The myoglobin-like haemoprotein leghaemoglobin (Lb I) from lupine root nodules has a great affinity to molecular oxygen and seems to be involved in O2-transport. Some ligands of low molecular weight are supposed to affect the haemoglobin (Hb) and myoglobin (Mo) function in O2-transport. To investigate this possibility for lupine Lb I, the affinity of this protein to cyanide (CN-), azide (N3-), fluoride (F-), thiocyanate (NCS-), imidazole (Im), nicotinic acid (NA), acetic acid has been investigated, using: 0.05 M MES, pH 5.2-6.5; 0.1 M Na-phosphate in 0.05 M Tris-buffer, pH 6.5-9.0. The affinity for Lb I to N3-, CN-, F- and NA (the Bohr effect) was found to be pH-dependent. The values of PK ionization for the groups affecting the ligands binding were determined. The positive correlation between the ligand affinity and the ligand power was found. Lb I appears to have the greatest ligand affinity constants when compared with other haemoproteins of this class.

[Acid-base equilibrium of yellow lupine ferrileghemoglobin. potentiometric studies]. / Kislotno-shchelochnye ravnovesiia ferrileggemoglobina zheltogo liupina. potentsiometricheskie issledovaniia.

Dissociation of ionizing groups in leghemoglobin from Lupinus Luteus in the wide pH range was studied by potentiometric titration. 16 + 8 groups were shown to the titrated at acid pH. One part of them are normally titrating groups and the other one is associated with some details of protein structure. At neutral pH 4 groups are titrated, the titration of 3 of the show histeresis. Five lysins are normally titrated at the alkaline pH. among them one is possibly responsible for an alkaline dissociation. 13 charged groups take part in the dissociation, 3-4 are titrated inreversibly. The experimental results are analyzed in terms of Linderstrom-Lang-Tanford representation and are discussed on the basis of primary and three-dimentional leghemoglobin structure.

[Heterogeneity of leghemoglobin from yellow lupine nodules]. / O geterogennosti leggemoglobinov iz kluben'kov zheltogo liupina.

A possibility is demonstrated to separate summary lupine leghemoglobins (which are salted out within 55--90% of ammonium sulphate saturation) into Lb I and Lb II components by means of ionic exchange chromatography on DEAE-cellulose. Lb I is eluted at lower ionic strength buffer than LbII, and differs from the latter in the form and the size of crystals. Both components have the same electrophoretic mobility and contain N-terminal glycine. LbII and LbI precipitate under gradual salting out within 55--75% and 78--90% of saturation respectively.