Structural insights into molecular function of the metastasis-associated phosphatase PRL-3.
Phosphatases and kinases are the cellular signal transduction enzymes that control protein phosphorylation. PRL phosphatases constitute a novel class of small (20 kDa), prenylated phosphatases with oncogenic activity. In particular, PRL-3 is consistently overexpressed in liver metastasis in colorectal cancer cells and represents a new therapeutic target. Here, we present the solution structure of PRL-3, the first structure of a PRL phosphatase. The structure places PRL phosphatases in the class of dual specificity phosphatases with closest structural homology to the VHR phosphatase. The structure, coupled with kinetic studies of site-directed mutants, identifies functionally important residues and reveals unique features, differentiating PRLs from other phosphatases. These differences include an unusually hydrophobic active site without the catalytically important serine/threonine found in most other phosphatases. The position of the general acid loop indicates the presence of conformational change upon catalysis. The studies also identify a potential regulatory role of Cys(49) that forms an intramolecular disulfide bond with the catalytic Cys(104) even under mildly reducing conditions. Molecular modeling of the highly homologous PRL-1 and PRL-2 phosphatases revealed unique surface elements that are potentially important for specificity.
Kozlov
Guennadi
G
Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada.
Cheng
Jing
J
Ziomek
Edmund
E
Banville
Denis
D
Gehring
Kalle
K
Ekiel
Irena
I
D000595:Amino Acid Sequence; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009363:Neoplasm Proteins; D019906:Nuclear Magnetic Resonance, Biomolecular; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
D017874:Immediate-Early Proteins; D009363:Neoplasm Proteins; C484730:PTP4A3 protein, human; D017027:Protein Tyrosine Phosphatases