1TF8: Streptomyces Griseus Aminopeptidase Complexed With L- Tryptophan

Citation:
Abstract
The bacterial aminopeptidase isolated from the extracellular extract of Streptomyces griseus (SGAP) is a double-zinc exopeptidase with a high preference for large hydrophobic amino-terminus residues. It is a monomer of a relatively low molecular weight (30 kDa), is heat-stable, displays a high and efficient catalytic turnover and its activity is modulated by calcium ions. Several free amino acids were found to inhibit the activity of SGAP in the millimolar concentration range and can therefore serve for the study of binding of both inhibitors and reaction products. The current study is focused on the X-ray crystallographic analysis of the SGAP complexes with L-tryptophan and p-iodo-L-phenylalanine, both at 1.30 A resolution. These two bulky inhibitory amino acids were found to bind to the active site of SGAP in very similar positions and orientations. Both of them bind to the two active-site zinc ions via their free carboxylate group, while displacing the zinc-bound water/hydroxide that is present in the native enzyme. Further stabilization of the binding of the amino-acid carboxylate group is achieved by its relatively strong interactions with the hydroxyl group of Tyr246 and the carboxylate group of Glu131. The binding is also stabilized by three specific hydrogen bonds between the amine group of the bound amino acid and enzyme residues Glu131, Asp160 and Arg202. These consistent interactions confirm the key role of these residues in the specific binding of the free amine of substrates and products, as proposed previously. The phenyl ring of Phe219 of the enzyme is involved in stacking interactions with the corresponding aromatic ring of the bound affector. This interaction seems to be important for the binding and orientation of the aromatic side chain within the specificity pocket. These structural results correlate well with the results obtained for the complexes of SGAP with other inhibitory amino acids and support the general catalytic mechanism proposed for this and related enzymes.
PDB ID: 1TF8Download
MMDB ID: 33146
PDB Deposition Date: 2004/5/27
Updated in MMDB: 2007/11
Experimental Method:
x-ray diffraction
Resolution: 1.3  Å
Source Organism:
Similar Structures:
Biological Unit for 1TF8: monomeric; determined by author and by software (PISA)
Molecular Components in 1TF8
Label Count Molecule
Protein (1 molecule)
1
Aminopeptidase
Molecule annotation
Chemicals (5 molecules)
1
2
2
1
3
2
* Click molecule labels to explore molecular sequence information.

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