Crystallization and preliminary crystallographic investigation of a low-pH native insulin monomer with flexible behaviour.
Insulin naturally aggregates as dimers and hexamers, whose structures have been extensively analysed by X-ray crystallography. Structural determination of the physiologically relevant insulin monomer, however, is an unusual challenge owing to the difficulty in finding solution conditions in which the concentration of insulin is high enough for crystallization yet the molecule remains monomeric. By utilizing solution conditions known to inhibit insulin assembly, namely 20% acetic acid, crystals of insulin in the monomeric state have been obtained. The crystals are strongly diffracting and a data set extending to 1.6 A has recently been collected. The crystals nominally belong to the space group I422, with unit-cell parameters a = b = 57.80, c = 54.61 A, giving rise to one molecule in the asymmetric unit. Preliminary electron-density maps show that whilst most of the insulin monomer is well ordered and similar in conformation to other insulin structures, parts of the B-chain C-terminus main chain adopt more than one conformation.
Zhang
Youshang
Y
Shanghai Institute of Biochemistry and Cell Biology, Academia Sinica, 320 Yue-Yang Road, Shanghai 200031, People's Republic of China.
Whittingham
Jean L
JL
Turkenburg
Johan P
JP
Dodson
Eleanor J
EJ
Brange
Jens
J
Dodson
G Guy
GG
D003460:Crystallization; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000737:chemistry*; D011487:Protein Conformation
D007328:Insulin