Expression, crystallization and preliminary X-ray studies of the PDZ domain of Dishevelled protein

Selenomethionine as an expressible handle for bioconjugations

Site-selective chemical bioconjugation reactions are enabling tools for the chemical biologist. Guided by a careful study of the selenomethionine (SeM) benzylation, we have refined the reaction to meet the requirements of practical protein bioconjugation. SeM is readily introduced through auxotrophic expression and exhibits unique nucleophilic properties that allow it to be selectively modified even in the presence of cysteine. The resulting benzylselenonium adduct is stable at physiological pH, is selectively labile to glutathione, and embodies a broadly tunable cleavage profile. Specifically, a 4-bromomethylphenylacetyl (BrMePAA) linker has been applied for efficient conjugation of complex organic molecules to SeM-containing proteins. This expansion of the bioconjugation toolkit has broad potential in the development of chemically enhanced proteins.

Post-Translational Backbone Engineering through Selenomethionine-Mediated Incorporation of Freidinger Lactams

Amino-γ-lactam (Agl) bridged dipeptides, commonly known as Freidinger lactams, have been shown to constrain peptide backbone topology and stabilize type II' β-turns. The utility of these links as peptide constraints has inspired new approaches to their incorporation into complex peptides and peptoids, all of which require harsh reaction conditions or protecting groups that limit their use on unprotected peptides and proteins. Herein, we employ a mild and selective alkylation of selenomethionine in acidic aqueous solution, followed by immobilization of the alkylated peptide on to bulk reverse-phase C₁₈ silica and base-induced lactamization in DMSO. The utilization of selenomethionine, which is readily introduced by synthesis or expression, and the mild conditions enable selective backbone engineering in complex peptide and protein systems.

Dapper, a Dishevelled-associated antagonist of beta-catenin and JNK signaling, is required for notochord formation

Dapper was isolated in a screen for proteins interacting with Dishevelled, a key factor in Wnt signaling. Dapper and Dishevelled colocalize intracellularly and form a complex with Axin, GSK-3, CKI, and beta-catenin. Overexpression of Dapper increases Axin and GSK-3 in this complex, resulting in decreased soluble beta-catenin and decreased activation of beta-catenin-responsive genes. Dapper also inhibits activation by Dishevelled of c-Jun N-terminal kinase (JNK), a component of beta-catenin-independent Frizzled signaling. Inhibition of Dapper activates both beta-catenin-responsive genes and an AP1-responsive promoter, demonstrating that Dapper is a general Dishevelled antagonist. Depletion of maternal Dapper RNA from Xenopus embryos results in loss of notochord and head structures, demonstrating that Dapper is required for normal vertebrate development.