The amino acid sequences of the biotinyl subunit essential for the association of transcarboxylase.

Abstract

tide 2-26 was shown to inhibit combination of the biotiny1 subunit with the outside subunit and thus retard combination with the central subunit and to cause a decrease in the enzymatic activity when compared with untreated subunits. Peptide 1-14 had no effect, showing it did not compete for the binding site on the outside subunit. When the 12 Su subunit was treated with either peptide, there was inhibition of formation of active enzyme, showing that each bound to the site on the central subunit. These results indicate that, of sequence 2-26,2-14 binds to the central subunit and 15-26 to the outside subunit or portions thereof. It is proposed that some residues in the central portion of sequence 2-26 are not bound to either the central or outside subunits and that the variation in distance which is observed in electron micrographs of transcarboxylase between the central and outside subunits results from this flexible portion of the sequence.