The interface of a membrane‐spanning leucine zipper mapped by asparagine‐scanning mutagenesis

Abstract

An oligo‐leucine sequence has previously been shown to function as an artificial transmembrane segment that efficiently self‐assembles in membranes and in detergent solution. Here, a novel technique, asparagine‐scanning mutagenesis, was applied to probe the interface of the self‐assembled oligo‐leucine domain. This novel approach identifies interfacial residues whose exchange to asparagine leads to enhanced self‐interaction of transmembrane helices by interhelical hydrogen bond formation. As analyzed by the ToxR system in membranes, the interface formed by the oligo‐leucine domain is based on a leucine‐zipper‐like heptad repeat pattern of amino acids. In general, the strongest impacts on self‐assembly were seen with asparagines located around the center of the sequence, indicating that interaction is be more efficient here than at the termini of the transmembrane domains.