Intramolecular interactions between the juxtamembrane domain and phosphatase domains of receptor protein-tyrosine phosphatase RPTPmu. Regulation of catalytic activity.
RPTPmu is a receptor-like protein-tyrosine phosphatase (RPTP) whose ectodomain mediates homotypic cell-cell interactions. The intracellular part of RPTPmu contains a relatively long juxtamembrane domain (158 amino acids; aa) and two conserved phosphatase domains (C1 and C2). The membrane-proximal C1 domain is responsible for the catalytic activity of RPTPmu, whereas the membrane-distal C2 domain serves an unknown function. The regulation of RPTP activity remains poorly understood, although dimerization has been proposed as a general mechanism of inactivation. Using the yeast two-hybrid system, we find that the C1 domain binds to an N-terminal noncatalytic region in RPTPmu, termed JM (aa 803-955), consisting of a large part of the juxtamembrane domain (120 aa) and a small part of the C1 domain (33 aa). When co-expressed in COS cells, the JM polypeptide binds to both the C1 and the C2 domain. Strikingly, the isolated JM polypeptide fails to interact with either full-length RPTPmu or with truncated versions of RPTPmu that contain the JM region, consistent with the JM-C1 and JM-C2 interactions being intramolecular rather than intermolecular. Furthermore, we find that large part of the juxtamembrane domain (aa 814-922) is essential for C1 to be catalytically active. Our findings suggest a model in which RPTPmu activity is regulated by the juxtamembrane domain undergoing intramolecular interactions with both the C1 and C2 domain.
Feiken
E
E
Division of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
van Etten
I
I
Gebbink
M F
MF
Moolenaar
W H
WH
Zondag
G C
GC
D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002384:Catalysis; D020134:Catalytic Domain; D002462:Cell Membrane / Q000201:enzymology*; D015723:Gene Library; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000378:metabolism*; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D014162:Transfection
D010446:Peptide Fragments; D011994:Recombinant Proteins; D017027:Protein Tyrosine Phosphatases; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2