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PR00859

Identifier
MTPROKARYOTE  [View Relations]  [View Alignment]  
Accession
PR00859
No. of Motifs
3
Creation Date
13-MAR-1998  (UPDATE 21-JUN-1999)
Title
Prokaryote metallothionein signature
Database References

PFAM; PF00131 metalthio
INTERPRO; IPR000518
Literature References
1. KAGI, J.H.R.
Overview of Metallothioneins.
METHODS ENZYMOL. 205 613-626 (1991).
 
2. KAGI, J.H.R. AND KOJIMA, Y.
Chemistry and biochemistry of metallothionein.
EXPERIENTIA SUPPL. 52 25-61 (1987).
 
3. KAGI, J.H.R. AND SCHAFFER, A.
Biochemistry of metallothionein.
BIOCHEMISTRY 27 8509-8515 (1988).
 
4. FOWLER, B.A., HILDEBRAND, C.E., KOJIMA, Y. AND WEBB, M.
Nomenclature of metallothionein.
EXPERIENTIA SUPPL. 52 21 (1987).
 
5. KOJIMA, Y.
Definitions and nomenclature of metallothioneins.
METHODS ENZYMOL. 205 8-10 (1991).
 
6. BINZ, P.-A. AND KAGI, J.H.R.
Molecular evolution of the metallothionein. Suggestions for a natural 
classification system.
FOURTH INTERNATIONAL MEETING ON METALLOTHIONEIN, KANSAS CITY (USA), 1997.

Documentation
Metallothioneins (MT) are small proteins that bind heavy metals, such as
zinc, copper, cadmium, nickel, etc.. They have a high content of cysteine
residues that bind the metal ions through clusters of thiolate bonds [1-3]
(http://www.unizh.ch/~mtpage/MT.html). An empirical classification into
three classes has been proposed by Fowler et al. [4] and Kojima [5]. Members
of class I are defined to include polypeptides related in the positions of
their cysteines to equine MT-1B, and include mammalian MTs as well as MTs 
from crustaceans and molluscs. Class II groups MTs from a variety of 
species, including sea urchins, fungi, insects and cyanobacteria. Class
III MTs are atypical polypeptides composed of gamma-glutamylcysteinyl
units [4]. 
 
This original classification system has been found to be limited, in the
sense that it does not allow clear differentiation of patterns of structural
similarities, either between or within classes. Consequently, all class I
and class II MTs (the proteinaceous sequences) have now been grouped into
families of phylogenetically-related and thus alignable sequences [6]
(http://www.unizh.ch/~mtpage/classif.html). This system subdivides the MT
superfamily into families, subfamilies, subgroups, and isolated isoforms
and alleles. 
 
The metallothionein superfamily comprises all polypeptides that resemble
equine renal metallothionein in several respects [4]: e.g., low molecular
weight; high metal content; amino acid composition with high Cys and low
aromatic residue content; unique sequence with characteristic distribution
of cysteines, and spectroscopic manifestations indicative of metal thiolate
clusters. A MT family subsumes MTs that share particular sequence-specific 
features and are thought to be evolutionarily related. The inclusion of a
MT within a family presupposes that its amino acid sequence is alignable 
with that of all members. Fifteen MT families have been characterised, each
family being identified by its number and its taxonomic range: e.g., Family
1: vertebrate MTs. 
 
Prokaryote family 14 MTs are 53-56 residue proteins, with 9 conserved 
cysteines. 
 
MTPROKARYOTE is a 3-element fingerprint that provides a signature for
family 14 metallothioneins. The fingerprint was derived from an initial
alignment of 3 sequences: the motifs were drawn from conserved regions
spanning the full alignment length - motif 1 contains 4 conserved metal-
binding Cys residues; and motifs 2 and 3 each include 2 Cys residues.
A single iteration on OWL30.0 was required to reach convergence, no further
sequences being identified beyond the starting set.
 
An update on SPTR37_9f identified a true set of 3 sequences.
Summary Information
3 codes involving  3 elements
0 codes involving 2 elements
Composite Feature Index
3333
2000
123
True Positives
MT_SYNP7      MT_SYNSP      MT_SYNVU      
Sequence Titles
MT_SYNP7    METALLOTHIONEIN (MT) - SYNECHOCOCCUS SP. (STRAIN PCC 7942) (ANACYSTIS NIDULANS R2). 
MT_SYNSP METALLOTHIONEIN (MT) - SYNECHOCOCCUS SP.
MT_SYNVU METALLOTHIONEIN (MT) - SYNECHOCOCCUS VULCANUS.
Scan History
OWL30_0    1  100  NSINGLE    
SPTR37_9f 1 100 NSINGLE
Initial Motifs
Motif 1  width=17
Element Seqn Id St Int Rpt
TSTTLVKCACEPCLCNV MT_SYNP7 1 1 -
TSTTLVKCACEPCLCNV MT_SYNSP 1 1 -
TTVTQMKCACPHCLCIV MT_SYNVU 1 1 -

Motif 2 width=17
Element Seqn Id St Int Rpt
PSKAIDRNGLYYCSEAC MT_SYNP7 19 1 -
PSKAIDRNGLYYCCEAC MT_SYNSP 19 1 -
LNDAIMVDGKPYCSEVC MT_SYNVU 19 1 -

Motif 3 width=17
Element Seqn Id St Int Rpt
ADGHTGGSKGCGHTGCN MT_SYNP7 36 0 -
ADGHTGGSKGCGHTGCN MT_SYNSP 36 0 -
ANGTCKENSGCGHAGCG MT_SYNVU 36 0 -
Final Motifs
Motif 1  width=17
Element Seqn Id St Int Rpt
TSTTLVKCACEPCLCNV MT_SYNP7 1 1 -
TSTTLVKCACEPCLCNV MT_SYNSP 1 1 -
TTVTQMKCACPHCLCIV MT_SYNVU 1 1 -

Motif 2 width=17
Element Seqn Id St Int Rpt
PSKAIDRNGLYYCSEAC MT_SYNP7 19 1 -
PSKAIDRNGLYYCCEAC MT_SYNSP 19 1 -
LNDAIMVDGKPYCSEVC MT_SYNVU 19 1 -

Motif 3 width=17
Element Seqn Id St Int Rpt
ADGHTGGSKGCGHTGCN MT_SYNP7 36 0 -
ADGHTGGSKGCGHTGCN MT_SYNSP 36 0 -
ANGTCKENSGCGHAGCG MT_SYNVU 36 0 -