JBC, Vol. 252, Issue 9, 2961-2966, May, 1977
Biological and biochemical properties of Phaseolus vulgaris isolectins
R. D. Leavitt, R. L. Felsted and N. R. Bachur
Affinity-purified phytohemagglutinin from red kidney bean resolves into
five isolectins by SP-Sephadex ion exchange chromatography. Recoveries
ranging from 30 to 130 mg of protein for each isolectin are easily
achieved. The isolectins have similar amino acid compositions which differ
only in threonine, lysine, and arginine. A distinguishing feature of the
amino acid composition is the total lack of sulfur-containing amino acids.
Each isolectin contains about 4% mannose and 2.2% N-acetyl-D-glucosamine.
All isolectins on electrophoresis form single protein bands under
denaturing and nondenaturing conditions in polyacrylamide gels, and all
have apparent subunit molecular weights of 33,000 by sodium dodecyl sulfate
polyacrylamide gel electrophoresis. The isolectins are also homogeneous by
ultracentrifugation and have apparent native molecular weights of 115,000
+/- 4,130, suggesting tetrameric quaternary structures. Whereas 80% of the
starting erythroagglutinin activity is recovered, one of the five
isolectins possesses 50% of that original activity. As sequentially eluted
from the ion exchange column, each isolectin displays progressively higher
erythroagglutinin and lower lymphocyte mitogenic activities. Based on their
relative biological activities, the isolectins are assigned the structures
L4, L3E1, L2E2, L1E3, and E4, where L and E represent lymphocyte- and
erythrocyte-reactive subunits, respectively, and the subscripts represent
the proposed subunit composition.