1T5A: Human Pyruvate Kinase M2

Four isozymes of pyruvate kinase are differentially expressed in human tissue. Human pyruvate kinase isozyme M2 (hPKM2) is expressed in early fetal tissues and is progressively replaced by the other three isozymes, M1, R, and L, immediately after birth. In most cancer cells, hPKM2 is once again expressed to promote tumor cell proliferation. Because of its almost ubiquitous presence in cancer cells, hPKM2 has been designated as tumor specific PK-M2, and its presence in human plasma is currently being used as a molecular marker for the diagnosis of various cancers. The X-ray structure of human hPKM2 complexed with Mg(2+), K(+), the inhibitor oxalate, and the allosteric activator fructose 1,6-bisphosphate (FBP) has been determined to a resolution of 2.82 A. The active site of hPKM2 is in a partially closed conformation most likely resulting from a ligand-induced domain closure promoted by the binding of FBP. In all four subunits of the enzyme tetramer, a conserved water molecule is observed on the 2-si face of the prospective enolate and supports the hypothesis that a proton-relay system is acting as the proton donor of the reaction (1). Significant structural differences among the human M2, rabbit muscle M1, and the human R isozymes are observed, especially in the orientation of the FBP-activating loop, which is in a closed conformation when FBP is bound. The structural differences observed between the PK isozymes could potentially be exploited as unique structural templates for the design of allosteric drugs against the disease states associated with the various PK isozymes, especially cancer and nonspherocytic hemolytic anemia.
PDB ID: 1T5ADownload
MMDB ID: 34060
PDB Deposition Date: 2004/5/3
Updated in MMDB: 2007/10
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 1T5A: tetrameric; determined by author and by software (PISA)
Molecular Components in 1T5A
Label Count Molecule
Proteins (4 molecules)
Pyruvate Kinase, M2 Isozyme(Gene symbol: PKM)
Molecule annotation
Chemicals (40 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB