1EF7: Crystal Structure Of Human Cathepsin X

BACKGROUND: Cathepsin X is a widespread, abundantly expressed papain-like mammalian lysosomal cysteine protease. It exhibits carboxy-monopeptidase as well as carboxy-dipeptidase activity and shares a similar activity profile with cathepsin B. The latter has been implicated in normal physiological events as well as in various pathological states such as rheumatoid arthritis, Alzheimer's disease and cancer progression. Thus the question is raised as to which of the two enzyme activities has actually been monitored. RESULTS: The crystal structure of human cathepsin X has been determined at 2.67 A resolution. The structure shares the common features of a papain-like enzyme fold, but with a unique active site. The most pronounced feature of the cathepsin X structure is the mini-loop that includes a short three-residue insertion protruding into the active site of the protease. The residue Tyr27 on one side of the loop forms the surface of the S1 substrate-binding site, and His23 on the other side modulates both carboxy-monopeptidase as well as carboxy-dipeptidase activity of the enzyme by binding the C-terminal carboxyl group of a substrate in two different sidechain conformations. CONCLUSIONS: The structure of cathepsin X exhibits a binding surface that will assist in the design of specific inhibitors of cathepsin X as well as of cathepsin B and thereby help to clarify the physiological roles of both proteases.
PDB ID: 1EF7Download
MMDB ID: 13005
PDB Deposition Date: 2000/2/7
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.67  Å
Source Organism:
Similar Structures:
Biological Unit for 1EF7: monomeric; determined by author
Molecular Components in 1EF7
Label Count Molecule
Protein (1 molecule)
Cathepsin X(Gene symbol: CTSZ)
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB