JBC, Vol. 252, Issue 20, 7062-7067, Oct, 1977
Lectins as probes of chromatin structure. Binding of concanavalin A to purified rat liver chromatin
W. B. Rizzo and M. Bustin
Concanavalin A (Con A) binds specifically to rat liver chromatin. The
extent of binding is directly proportional to both chromatin and
concanavalin A concentration. It is reversible and inhibited by specific
sugars for which concanavalin A has a binding site. Scatchard analysis
reveals the presence of one type of Con A-binding site, with an apparent
dissociation constant of 3 X 10(-7) M. A maximum of 10 pmol of Con A binds
to 10 microgram of chromatin, indicating an average of one binding
site/1400 base pairs of DNA. To identify the polypeptide chains which
contain Con A-binding sites, chromosomal proteins were separated by
electrophoresis on polyacrylamide gels containing sodium dodecyl sulfate.
Con A receptors were localized by incubating the gel in 125I-Con A and
subsequent autoradiography. Three major polypeptide bands which bind Con A
were identified among the nonhistone chromosomal proteins. The apparent
molecular weights of these glycoproteins are 135,000, 125,000, and 69,000.
We suggest that lectins may serve as probes for the study of the
organization of specific components in chromatin.
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