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Article

Mycosamine Orientation of Amphotericin B Controlling Interaction with Ergosterol: Sterol-Dependent Activity of Conformation-Restricted Derivatives with an Amino-Carbonyl Bridge

Supporting Info

Nobuaki Matsumori, Yuri Sawada, and Michio Murata*

Contribution from the Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan

J. Am. Chem. Soc., 2005, 127 (30), pp 10667–10675

DOI: 10.1021/ja051597r

Publication Date (Web): July 12, 2005

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, murata@ch.wani.osaka-u.ac.jp

Abstract

Amphotericin B (AmB 1) is known to assemble together and form an ion channel across biomembranes. The antibiotic consists of mycosamine and macrolactone moieties, whose relative geometry is speculated to be determinant for the drug's channel activity and sterol selectivity. To better understand the relationship between the amino-sugar orientation and drug's activity, we prepared conformation-restricted derivatives 2−4, in which the amino and carboxyl groups were bridged together with various lengths of alkyl chains. K⁺ influx assays across the lipid-bilayer membrane revealed that ergosterol selectivity was markedly different among derivatives; short-bridged derivative 2 almost lost the selectivity, while 3 showed higher ergosterol preference than AmB itself. Monte Carlo conformational analysis of 2−4 based on NOE-derived distances indicated that the amino-sugar moiety of 2 comes close to C41 because of the short bridge, whereas those of 3 and 4 are pointing outward. The mutual orientation of the amino-sugar moiety and macrolide ring is so rigid in derivatives 2 and 3 that these conformations should be unchanged upon complex formation in lipid membranes. These results strongly suggest that the large difference in sterol preference between derivatives 2 and 3 is ascribed to the different orientation of amino-sugar moieties. These findings allowed us to propose a simple model accounting for AmB−sterol interactions, in which hydrogen bonding between 2‘-OH of AmB and 3β-OH of ergosterol plays an important role.