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Two distinct types of cell surface folic acid‐binding proteins in Dictyostelium discoideum
Author(s) -
De Wit R.J.W.
Publication year - 1982
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(82)80786-2
Subject(s) - dictyostelium discoideum , folic acid , cooperativity , chemistry , chemotaxis , biochemistry , cooperative binding , receptor , binding site , medicine , gene
Folic acid is degraded too fast by Dictyostelium discoideum to study binding of this ligand to cell surface binding proteins. Folate deaminase activity was inhibited in the presence of 3.3 × 10 −4 M 8‐azaguanine. This inhibitor enabled us to detect two folate binding proteins. One type bound folic acid and deamino‐folic acid with the same affinity ( K 0.5 = 3–6 × 10 −7 M) and apparently negative cooperativity. Binding to only this type was observed if 8‐azaguanine was omitted. The second type bound folic acid noncooperatively with K d = 7 × 10 −7 M. Deamino‐folic acid did not compete even at a 1000‐fold excess. This type may correspond to the chemotactic receptor.