 |
PDBsum entry 1ekf
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
The structure of human mitochondrial branched-Chain aminotransferase.
|
|
|
Authors
|
|
N.Yennawar,
J.Dunbar,
M.Conway,
S.Hutson,
G.Farber.
|
|
|
Ref.
|
|
Acta Crystallogr D Biol Crystallogr, 2001,
57,
506-515.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
X-ray crystal structures of three forms of human mitochondrial branched-chain
aminotransferase (BCAT) were solved by molecular-replacement methods, using
Escherichia coli BCAT as the search model. The enzyme is a homodimer and the
polypeptide chain of each monomer has two domains. The small domain is composed
of residues 1--175 and the large domain is composed of residues 176--365. The
active site is close to the dimer interface. The 4'-aldehyde of the PLP cofactor
is covalently linked to the epsilon-amino group of the active-site lysine,
Lys202, via a Schiff-base linkage in two of the structures. In the third
structure, the enzyme is irreversibly inactivated by Tris. The overall fold of
the dimer in human mitochondrial BCAT is similar to the structure of two
bacterial enzymes, E. coli BCAT and D-amino acid aminotransferase (D-AAT). The
residues lining the putative substrate-binding pocket of human BCAT and D-AAT
are completely rearranged to allow catalysis with substrates of opposite
stereochemistry. In the case of human mitochondrial branched-chain
aminotransferase, a hydrogen-bond interaction between the guanidinium group of
Arg143 in the first monomer with the side-chain hydroxyl of Tyr70 in the second
monomer is important in the formation of the substrate-binding pocket.
|
|
|
|
|
|
|
|
Figure 2.
Figure 2 Active-site density of BCAT inhibited by Tris. The map
was calculated from a structure that does not contain Tris. This
is the first example in the Protein Data Bank where a buffer has
formed a covalent intermediate with an enzyme active site.
|
|
Figure 6.
Figure 6 (a) Active-site superposition of E. coli BCAT (thinner
bonds and smaller residue labels) with human BCATm (thicker
bonds and larger residue labels). The side chains are conserved
and their orientation is very similar. (b) Active-site
superposition of D-AAT (thinner bonds and smaller residue
labels) with human BCATm (thicker bonds and larger residue
labels). Only the side chains interacting with the PLP are
similar in nature and have comparable conformation.
|
|
|
|
|
|
The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(2001,
57,
506-515)
copyright 2001.
|
|
|
Secondary reference #1
|
|
|
Title
|
|
Cloning of the rat and human mitochondrial branched chain aminotransferases (bcatm).
|
|
|
Authors
|
|
R.K.Bledsoe,
P.A.Dawson,
S.M.Hutson.
|
|
|
Ref.
|
|
Biochim Biophys Acta, 1997,
1339,
9.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
|
|
|
|
