ABSTRACT
The DNA binding and in vitro cytotoxicity of the dinuclear Ir(III) polypyridyl complexes [{(eta(5)-C(5)Me(5))Ir(dppz)}(2)(mu-pyz)](CF(3)SO(3))(4)1 and [{(eta(5)-C(5)Me(5))Ir(pp)}(2)(mu-4,4'-bpy)](CF(3)SO(3))(4)2-4 (pp=dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), dipyrido[2,3-a:2',3'-c]phenazine (dppz), benzo[i]dipyrido[3,2-a:2',3'-c]phenazine (dppn)) with the rigid bridging ligands pyrazine (pyz) or 4,4'-bipyridine (4,4'-bpy) have been studied. Stable intercalative binding into CT DNA (calf thymus DNA) is indicated for the dppz complexes 1 and 3 by induced negative CD bands at about 300nm and large viscosity increases, with the individual measurements being in accordance with intrastrand bis-intercalation for 3 and mono-intercalation for 1. The observed interruption of specific interresidue NOE cross peaks from the relevant nucleobase H6/H8 protons to the sugar H2'/H2'' protons of the preceding nucleotide is in accordance with bis-intercalation of complex 3 between the C3G18 and G4C17 base pairs and the T5A16 and A6T15 base pairs of the decanucleotide d(5'-CGCGTAGGCC-3'). Complexes 1 and 3 exhibit a greatly improved uptake by HT-29 (colon carcinoma) cells and significantly improved in vitro IC(50) values of 1.8+/-0.1 and 3.8+/-0.1microM towards this cell line in comparison to the mononuclear complex [(eta(5)-C(5)Me(5))IrCl(dppz)](CF(3)SO(3)) (IC(50)=7.4+/-0.9microM).
Subject(s)
Cytotoxins , DNA/chemistry , Intercalating Agents , Iridium , Organometallic Compounds , Animals , Cattle , Cell Line, Tumor , Cytotoxins/chemical synthesis , Cytotoxins/chemistry , Cytotoxins/pharmacology , Humans , Intercalating Agents/chemical synthesis , Intercalating Agents/chemistry , Intercalating Agents/pharmacology , Iridium/chemistry , Iridium/pharmacology , Organometallic Compounds/chemical synthesis , Organometallic Compounds/chemistry , Organometallic Compounds/pharmacologyABSTRACT
Psb27 is a membrane-extrinsic subunit of photosystem II (PSII) where it is involved in the assembly and maintenance of this large membrane protein complex that catalyzes one of the key reactions in the biosphere, the light-induced oxidation of water. Here, we report for the first time the structure of Psb27 that was not observed in the previous crystal structures of PSII due to its transient binding mode. The Psb27 structure shows that the core of the protein is a right-handed four-helix bundle with an up-down-up-down topology. The electrostatic potential of the surface generated by the amphipathic helices shows a dipolar distribution which fits perfectly to the major PsbO binding site on the PSII complex. Moreover, the presented docking model could explain the function of Psb27, which prevents the binding of PsbO to facilitate the assembly of the Mn(4)Ca cluster.
Subject(s)
Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Photosystem II Protein Complex/chemistry , Photosystem II Protein Complex/metabolism , Synechocystis/chemistry , Synechocystis/metabolism , Arabidopsis/chemistry , Arabidopsis/microbiology , Arabidopsis/radiation effects , Arabidopsis Proteins/chemistry , Arabidopsis Proteins/metabolism , Crystallography, X-Ray , Light/adverse effects , Photosystem II Protein Complex/biosynthesis , Photosystem II Protein Complex/radiation effects , Protein Binding/radiation effects , Protein Structure, Secondary , Protein Subunits/chemistry , Protein Subunits/metabolism , Solutions , Static Electricity , Surface Properties , Synechocystis/radiation effectsABSTRACT
Nucleoporin (Nup) 153 is a highly mobile, multifunctional, and essential nuclear pore protein. It contains four zinc finger motifs that are thought to be crucial for the regulation of transport-receptor/cargo interactions via their binding to the small guanine nucleotide binding protein, Ran. We found this interaction to be independent of the phoshorylation state of the nucleotide. Ran binds with the highest affinity to the second zinc finger motif of Nup153 (Nup153ZnF2). Here we present the crystal structure of this complex, revealing a new type of Ran-Ran interaction partner interface together with the solution structure of Nup153ZnF2. According to our complex structure, Nup153ZnF2 binding to Ran excludes the formation of a Ran-importin-beta complex. This finding suggests a local Nup153-mediated Ran reservoir at the nucleoplasmic distal ring of the nuclear pore, where nucleotide exchange may take place in a ternary Nup153-Ran-RCC1 complex, so that import complexes are efficiently terminated.
Subject(s)
Nuclear Pore Complex Proteins/chemistry , Zinc Fingers , ran GTP-Binding Protein/chemistry , Active Transport, Cell Nucleus , Amino Acid Sequence , Animals , Binding Sites , Cell Nucleus/metabolism , Crystallography, X-Ray , Guanosine Diphosphate/chemistry , Guanosine Triphosphate/chemistry , Models, Molecular , Molecular Sequence Data , Nuclear Magnetic Resonance, Biomolecular , Nuclear Pore/metabolism , Nuclear Pore Complex Proteins/metabolism , Rats , Sequence Homology, Amino Acid , ran GTP-Binding Protein/metabolismABSTRACT
Protein tyrosine phosphatase-basophil like (PTP-BL) represents a large multi domain non-transmembrane scaffolding protein that contains five PDZ domains. Here we report the backbone assignments of the PDZ2/PDZ3 tandem domain of PTP-BL. These assignments now provide a basis for the detailed structural investigation of the interaction between the PDZ domains 2 and 3 of PTP-BL. It will lead to a better understanding of the proposed scaffolding function of this tandem domain in multi-protein complexes assembled by PTB-BL.
