NMR analysis of the structure and metal sequestering properties of metallothioneins. [Mammals; Scylla serrata]
/sup 113/Cd-NMR studies have been used to elucidate the structure of the metal-binding sites in mammalian and invertebrate (Scylla serrata) metallothioneins (MTs). Chemical shift data have shown that all Cd ions are tetrahedrally coordinated to four cysteine thiolate ligands with single cysteinyl sulfurs bridging adjacent metals. Homonuclear decoupling experiments have shown that the 7 g-atoms of metal bound per mole of mammalian protein are located in a three- and a four-metal cluster while the 6 g-atoms of metal in the invertebrate MT are located in two three-metal clusters. The different metal binding affinities of the two mammalian clusters have been determined by /sup 113/Cd-NMR. The three-metal cluster prefers Cu > Zn > Cd whereas exactly the reverse order applies in the four-metal cluster. Proteolytic cleavage of the protein produced a 32-residue fragment which contained the four-metal cluster and demonstrated the presence of two separate domains in the protein. 500 MHz /sup 1/H-NMR has been employed to elucidate the arrangement of these metal clusters in the tertiary structure of the protein. The /sup 1/H resonances were assigned from their scalar and dipolar connectivities obtained from extensive one and two-dimensional NMR experiments. A specific application of 2D correlation spectroscopy (COSY) to the assignment of the /sup 1/H resonances in crab MT-1 is discussed. A molecular model, representing the three-dimensional solution structure of this protein, has been constructed based on an analysis of all these data. Detailed structural features of this model are discussed, with particular emphasis on their relationship to the function and evolution of the protein. 57 references, 8 figures.
- Research Organization:
- Yale Univ., New Haven, CT
- OSTI ID:
- 5765867
- Journal Information:
- Environ. Health Perspect.; (United States), Journal Name: Environ. Health Perspect.; (United States) Vol. 54; ISSN EVHPA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
AFFINITY
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL FUNCTIONS
CADMIUM
CADMIUM 113
CADMIUM ISOTOPES
CARBOXYLIC ACIDS
CHEMICAL BONDS
COPPER
CYSTEINE
DATA
ELEMENTS
EVEN-ODD NUCLEI
EXPERIMENTAL DATA
FUNCTIONS
INFORMATION
INTERMEDIATE MASS NUCLEI
INVERTEBRATES
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MAGNETIC RESONANCE
MAMMALS
METALLOPROTEINS
METALLOTHIONEIN
METALS
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PROTEINS
RADIOISOTOPES
RESONANCE
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS
STRUCTURAL MODELS
THIOLS
TRACER TECHNIQUES
TRANSITION ELEMENTS
VERTEBRATES
YEARS LIVING RADIOISOTOPES
ZINC