Yeas t dolichyl-P-mannose synthase and a number of other enzymes that interact with dolichol or dolichyl-P as substrates contain a highly conserved amino-acid sequence that has been proposed as a potential dolichol recognition sequence [Albright, C.F., Orlean, P. & Robbins, P.W. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 7366-7369]. In dolichyl-P-mannose synthase/ the most highly conserved amino-acid residues of this domain were modified by site directed mutagenesis, and for one construct the sequence was completely deleted. Enzymes containing the site directed modifications/ and the deletion mutant, were found to retain catalytic activity, and all of the modified enzymes had the same apparent affinity for Dol-P as wild type enzyme when assayed in a phospholipid matrix. Based on these results, the amino-acid composition and sequence of the conserved domain are not critically important for the recognition and binding of Dol-P when the synthase is reconstituted in a lipid matrix.
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