Protein-tyrosine phosphatase receptor type Z (Ptprz) has multiple substrate proteins, including G protein-coupled receptor kinase-interactor 1 (Git1), membrane-associated guanylate kinase, WW and PDZ domain-containing 1 (Magi1), and GTPase-activating protein for Rho GTPase (p190RhoGAP). We have identified a dephosphorylation site at Tyr-1105 of p190RhoGAP; however, the structural determinants employed for substrate recognition of Ptprz have not been fully defined. In the present study, we revealed that Ptprz selectively dephosphorylates Git1 at Tyr-554, and Magi1 at Tyr-373 and Tyr-858 by in vitro and cell-based assays. Of note, the dephosphorylation of the Magi1 Tyr-858 site required PDZ domain-mediated interaction between Magi1 and Ptprz in the cellular context. Alignment of the primary sequences surrounding the target phosphotyrosine residue in these three substrates showed considerable similarity, suggesting a consensus motif for recognition by Ptprz. We then estimated the contribution of surrounding individual amino acid side chains to the catalytic efficiency by using fluorescent peptides based on the Git1 Tyr-554 sequence in vitro. The typical substrate motif for the catalytic domain of Ptprz was deduced to be Glu/Asp-Glu/Asp-Glu/Asp-Xaa-Ile/ Val-Tyr(P)-Xaa (Xaa is not an acidic residue). Intriguingly, a G854D substitution of the Magi1 Tyr-858 site matching better to the motif sequence turned this site to be susceptible to dephosphorylation by Ptprz independent of the PDZ domainmediated interaction in cells. Furthermore, we found by database screening that the substrate motif is present in several proteins, including paxillin at Tyr-118, its major phosphorylation site. Expectedly, we verified that Ptprz efficiently dephosphorylates paxillin at this site in cells. Our study thus provides key insights into the molecular basis for the substrate recognition of Ptprz.Protein-tyrosine phosphorylation is a dynamic process governed by the balanced actions of protein-tyrosine kinases (PTKs), 2 and protein-tyrosine phosphatases (PTPs), and critical to the regulation of numerous physiological processes (for review, see Ref. 1). The specificity of the signal transduction depends on the ability of each PTK or PTP to phosphorylate or dephosphorylate precisely particular sites on specific substrates, respectively. Elucidation of the specificity for individual PTPs has been an important subject of investigation; however, even the identification of PTP substrates is still methodologically difficult. To our knowledge, substrate specificity of PTPs has been characterized only for PTP1B (2).Receptor-like PTPs (RPTPs) are a structurally and functionally diverse family of enzymes comprised of eight subfamilies. PTP receptor type Z (Ptprz, also called PTP or RPTP␤) is a RPTP classified in the R5 subfamily together with Ptprg (PTP␥). Three isoforms of Ptprz are generated by alternative splicing from a single Ptprz gene: the two transmembrane isoforms Ptprz-A and Ptprz-B and the secretory isoform Ptprz-S (also known as phosphacan...

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Catalytic dehydrogenative silylation of terminal alkynes with hydrosilanes has been achieved by using divalent Yb−imine complexes. The reaction with mono-, di-, and trihydrosilanes gave the corresponding alkynylsilanes in good yields. α,ω-Diynes were similarly silylated at both termini. Thus, oligomers were obtained from the diynes and dihydrosilanes. In addition, it has been found that the imine complexes exhibit catalytic activity for redistribution of the silyl groups of the alkynylsilanes and for Si−Si bond fission of disilanes.

A dianionic lanthanoid(II)−imine azametallacyclopropane complex, [Yb(η2-Ph2CNPh)(hmpa)3] (hmpa = hexamethylphosphoramide), has been directly synthesized by the reaction of ytterbium metal with N-(diphenylmethylidene)aniline in THF/HMPA and structurally characterized by X-ray analysis.

Poly[2,7-(9-oxo-9-phosphafluorenylene)-alt-co-(1,4-arylene)]s, readily prepared from 2,7-dibromo-9-oxo-9-phosphafluorenes and arylene bisboronates, behaved as extended π-conjugated polymers in the UV–vis absorption spectroscopy and displayed green-blue fluorescence with high quantum yields. Cyclic voltammetry revealed the polymers exhibited electrochromic behaviors and afforded a bandgap of ca. 2.8 eV, consistent with the value from the absorption edge.