Journal:Acta Cryst F:S1744309112003326

The use of whole insect larvae as a source of recombinant proteins offers a more cost-effective method of producing large quantities of human proteins than conventional cell-culture approaches. Human carboxylesterase 1 (rhCES1) has been produced in and isolated from whole ''Trichoplusia ni'' larvae. The recombinant protein was crystallized and its structure was solved to 2.2 Å resolution. The current structure of rhCES1 represents the first published hexagonal crystal form, despite the fact that all other published examples of hCES1 structures consist of a hexamer in the asymmetric unit. <scene name='Journal:Acta_Cryst_F:1/Cv/4'>The trimer of subunits sits around one of the threefold axes</scene> found in this space group, while the three twofold axes at z = 1/4 that intersect on this axis complete the <scene name='Journal:Acta_Cryst_F:1/Cv/5'>hexamer</scene>. An <scene name='Journal:Acta_Cryst_F:1/Cv/6'>alignment of the A chain from PDB entry 2h7c with the asymmetric unit reported here</scene> gave an r.m.s. deviation of 0.42 Å for 522 Cα atoms ([[2h7c]] <font color='red'><b>is colored in red</b></font> and <span style="color:lime;background-color:black;font-weight:bold;">rhCES1 is in green</span>). An r.m.s. value of 0.47 Å (3132 Cα atoms) was obtained for the entire [[2h7c]] hexamer superposed with the symmetry-generated rhCES1 hexamer, indicating that the quaternary structure is essentially identical in these crystal forms isolated from cultured Sf21 cells, supporting the use of this expression system to produce recombinant enzymes for crystallization studies.