Marine mussels affix themselves to surfaces with a protein-based, cross-linked adhesive. Studies with mussel glue, extracted protein, and peptide models show an Fe(DOPA) 3 cross-link, which is key for the generation of this common biological material. For more information, see the Communication by J. J. Wilker and co-workers following pages.

Interactions between metals and catechol (1,2-dihydroxybenzene) or other ortho-dihydroxy moieties are being found in an increasing number of biological systems with functions ranging from metal ion internalization to biomaterial synthesis. Although metal-catecholate interactions have been studied in the past, we present the first systematic study of an array of these compounds, all prepared under identical conditions. We report the ultraviolet-visible absorption (UV-vis) spectra for catecholate and tironate complexes of the first row transition elements. Generation and identification of these species were accomplished by preparing aqueous solutions with varied ligand:metal ratios and subsequently titrating with base (NaOH). Controlled ligand deprotonation and metal binding resulted in sequential formation of complexes with one, two, and sometimes three catecholate or tironate ligands bound to a metal ion. We prepared the mono-, bis- and tris-catecholates and -tironates of Fe(3+), V(3+), V(4+)and Mn(3+), the mono- and bis-catecholates and -tironates of Cu(2+), Co(2+), Ni(2+), Zn(2+), Cr(2+) and Mn(2+), and several Ti(4+) and Cr(3+) species. The UV-vis spectra of each complex are described, some of which have not been reported previously. These data can now be applied to characterization of biological metal-catecholate systems.

SUMMARY A high-throughput RNA interference (RNAi) screen targeting 542 genes of the human kinome was used to discover regulators of RNAi. Here we report that the proto-oncogene Akt-3/PKBγ (Akt3) phosphorylates Argonaute 2 (Ago2) at Ser387 which down-regulates cleavage and up-regulates translational repression of endogenous microRNA (miRNA)-targeted mRNAs. We further demonstrate that Akt3 co-immunoprecipitates with Ago2 and that phosphorylation of Ago2 at Ser387 facilitates its interaction with GW182 and localization to cytoplasmic P-bodies, where miRNA-targeted mRNAs are thought to be stored and degraded. Therefore, Akt3-mediated phosphorylation of Ago2 is a molecular switch between target mRNA cleavage and translational repression activities of Ago2.

A diverse array of biological systems incorporate 3,4-dihydroxyphenlyalanine (DOPA) into proteins and small molecules for cross-linking and material generation. Marine worm eggshells, sea squirt wound plugs, and marine mussel adhesives may all be formed by combining DOPA-containing molecules with high levels of metals. In order to provide model systems for characterizing these biomaterials, we carried out a study on metal binding to a DOPA-containing peptide. Ultraviolet-visible absorption spectra are presented for the AdopaTP peptide binding to Fe3+, V3+, VO2+, Mn3+, Ti4+, Cu2+, Co2+, and Ni2+ in mono, bis, and where applicable, tris coordination modes. Association constants were determined for selected metal ions binding to the peptide. In general, the spectroscopic and binding properties of this DOPA-containing peptide were found to be similar to those of catechol.

Eiserner Griff: Ein Protein wirkt als Klebstoff beim Anheften von Muscheln an Steine. Eisen‐Zentren vernetzen die Makromoleküle, indem sie die Dihydroxyphenyl‐Einheiten von drei dopa‐Liganden koordinieren (siehe Bild). Übergangsmetallionen werden also auch in nichtkristalline Biomaterialien als feste Bestandteile eingebaut.