Chemical modifications of metallothionein. Preparation and characterization of polymers

Abstract

Reaction of rat liver metallothionein-II with two bifunctional cross-linking reagents, glutaraldehyde and dimethyl suberimidate, produces high yields of polymeric species. It is argued that cross-linking is trapping preformed aggregates of the protein, which therefore represent a stabilized quaternary structure of metallothionein. The two polymeric species differ in a number of respects. With dimethyl suberimidate, the polymer retains all metal-binding sites of the monomer, and has an unaltered isoelectric point. Reaction with glutaraldehyde causes loss of one or two Cd2+/Zn2+-binding sites and elevates the pI. Both species are nearly spherical aggregates, in contrast with the highly asymmetrical metallothionein. Both polymers are linked through lysine residues, and the thiol groups remain reduced. The biological significance of these aggregates is discussed.

Increased Zinc and Manganese in Parallel with Neurodegeneration, Synaptic Protein Changes and Activation of Akt/GSK3 Signaling in Ovine CLN6 Neuronal Ceroid Lipofuscinosis

“…The expression of both the 7 kDa form (calculated molecular weight form) and polymerized high molecular forms migrating at approximately 23 kDa and 50 kDa were increased in the affected brain. These higher molecular weight forms have been consistently reported in diverse tissues and animals [31]–[33].…”

Lowering of lipid peroxidation and acute toxicity of bromobenzene by a polymeric form of zinc-metallothionein

“…Purification and characterization of Zn-MT from rat liver (the protein was dissolved in the standard 10 mM Tris-HC1 buffer, pH 7.4) were described elsewhere [1]. Thus, the polymeric form consisted of 8-10 Zn-MT monomers (6-7 kD) [6,11]. After electrophoresis of the polymer under denaturating conditions, a wide band corresponding to a molecular weight range of 61-70 kD was obtained, which is consistent with the published data [11].…”

“…A polymeric form of Zn-MT, which is more stable in the organism, was obtained by a reported method [11]: lysine residues were cross-linked by glutaric aldehyde (Fluka), and the protein was separated from the low-molecular form on Sephadex G-75. Thus, the polymeric form consisted of 8-10 Zn-MT monomers (6-7 kD) [6,11]. Thus, the polymeric form consisted of 8-10 Zn-MT monomers (6-7 kD) [6,11].…”

“…MT synthesis is induced by toxic influences, which raises animals' resistance to them [6]. Thus, the polymeric form consisted of 8-10 Zn-MT monomers (6-7 kD) [6,11]. In fact, MT preparations do inhibit lipid peroxidation (LPO) in vitro [12].…”

Further accumulation of Cd in renal cellular membranes caused by administration of desferrioxamine to Cd-burdened rats

“…Rats received subcutaneous injections of the Cd solution (3.0 mg Cd/kg body weight (bw) per day) on days 0-7, 10,16,17 and the DFO solution (50 mg/kg bw/day) on days 8-14; the dose of DFO was equivalent to that used clinically. 4-7 Control animals received subcutaneous injections of an equivalent volume of saline given in an identical manner.…”