Self-assembly of proteins into designed networks.

A C4-symmetric tetrameric aldolase was used to produce a quadratic network consisting of the enzyme as a rigid four-way connector and stiff streptavidin rods as spacers. Each aldolase subunit was furnished with a His6 tag for oriented binding to a planar surface and two tethered biotins for binding streptavidin in an oriented manner. The networks were improved by starting with composite units and also by binding to nickel-nitrilotriacetic acid-lipid monolayers. The mesh was adjustable in 5-nanometer increments. The production of a net with switchable mesh was initiated with the use of a calcium ion-containing beta-helix spacer that denatured on calcium ion depletion.