On the quaternary structure of leucine aminopeptidase.

Small crystals of leucine aminopeptidase were prepared in 2 percent ammonium molybdate. Single molecules were contrasted with 2 percent potassium silico tungstate which gave better contrast and preservation of enzyme activity than ammonium molybdate. The six subunits of the enzyme consist of a spheroidal "head" and some "tail-like" material, which connects the "heads" in pairs. The subunits are arranged at the vertices of either a right triangular prism or of an oblique prism twisted by 42 degree (symmetry 32).