Abstract
Esterase A4 (EA4) is a timer protein found in diapause eggs of the silkworm Bombyx mori. The gene for this metalloglycoprotein was cloned from B. mori eggs and expressed using a baculovirus expression system in silkworm pupae. Crystals of the purified protein have been grown that diffract to beyond 2.1 A resolution at 100 K using synchrotron radiation. The protein crystals belong to space group P2(1), with unit-cell parameters a = 47.1, b = 73.9, c = 47.4 A, beta = 104.1 degrees. With one dimer per asymmetric unit, the crystal volume per unit protein weight (V(M)) is 2.3 A3 Da(-1) and the solvent content is 47%.