Three-dimensional structure and dynamics of a brain specific growth inhibitory factor: metallothionein-3.
The brain specific member of the metallothionein (MT) family of proteins, metallothionein-3, inhibits the growth and survival of neurons, in contrast to the ubiquitous mammalian MT isoforms, MT-1 and MT-2, that are found in most tissues and are thought to function in metal ion homeostasis and detoxification. Solution NMR was utilized to determine the structural and dynamic differences of MT-3 from MT-1 and 2. The high-resolution solution structure of the C-terminal alpha-domain of recombinant mouse MT-3 revealed a tertiary fold very similar to MT-1 and 2, except for a loop that accommodates an acidic insertion relative to these isoforms. This loop was distinguished from the rest of the domain by dynamics of the backbone on the nano- to picosecond time-scale shown by (15)N relaxation studies and was identified as a possible interaction site with other proteins. The N-terminal beta-domain contains the region responsible for the growth inhibitory activity, a CPCP tetrapeptide close to the N-terminus. Because of exchange broadening of a large number of the NMR signals from this domain, homology modeling was utilized to calculate models for the beta-domain and suggested that while the backbone fold of the MT-3 beta-domain is identical to MT-1 and 2, the second proline responsible for the activity, Pro9, may show structural heterogeneity. (15)N relaxation analyses implied fast internal motions for the beta-domain. On the basis of these observations, we conclude that the growth inhibitory activity exhibited by MT-3 is a result of a combination of local structural differences and global dynamics in the beta-domain.
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Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA.
Zangger
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Armitage
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D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000166:cytology / Q000502:physiology*; D002104:Cadmium / Q000737:chemistry / Q000378:metabolism; D002455:Cell Division; D002470:Cell Survival; D003001:Cloning, Molecular; D003196:Computer Graphics; D004926:Escherichia coli; D006131:Growth Inhibitors / Q000737:chemistry*; D008322:Mammals; D008668:Metallothionein / Q000737:chemistry*; D000090023:Metallothionein 3; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000502:physiology; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D011487:Protein Conformation; D020033:Protein Isoforms / Q000737:chemistry; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D006131:Growth Inhibitors; D000090023:Metallothionein 3; C000715430:Mt3 protein, mouse; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D011994:Recombinant Proteins; D002104:Cadmium; D008668:Metallothionein