Cysteine-independent polymerization of metallothioneins in solutions and in crystals

Polymerization of metallothioneins is one of the usually encountered puzzle s during the research process of metallothioneins' structure and function. Our work focuses on the cysteine independently occurred polymerization from metallothioneins monomers in different milieus, while it leaves out the ag gregation caused by the oxidation of cysteine. because the Latter circumsta nce is the result of purification lapsus. After the purification of metallo thioneins monomers, a dynamic light-scattering technique is used to detect the polymerized states of rabbit liver metallothionein I and Ii in differen t buffers, which is the first systematical detection of polymerized states of metallothioneins in solutions. The effects of different compositions of each buffer are discussed in details. Steric complementarity, hydrophobic, and electrostatic interaction characteristics are studied. following the mo deling of monomers and relevant polymers of rat metallothionein II, rabbit liver metallothionein I and II. These theoretical calculations are the firs t complete computer simulations on different factors affecting metallothion eins' polymerization. A molecular recognition mechanism of metallothioneins ' polymerization in solutions is proposed on the bases of experimental resu lts and theoretical calculations. Preliminary X-ray studies of two crystal forms of rabbit liver metallothionein II are compared with the crystal stru cture of rat metallothionein II, and the polymerized states in crystal pack ing are discussed with the: knowledge of polymerization of metallothioneins in solutions. The hypothesis, which is consistent with theoretical calcula tions and experimental results, is expected to construct a connection betwe en the biochemical characteristics and physiological Functions of metalloth ioneins. and this research may give some enlightenment to the topics of pro tein polymerizations.