Modular HIV-1 Capsid Assemblies Reveal Diverse Host-Capsid Recognition Mechanisms.

The HIV-1 capsid is an ordered protein shell that houses the viral genome during early infection. Its expansive surface consists of an ordered and interfacing array of capsid protein hexamers and pentamers that are recognized by numerous cellular proteins. Many of these proteins recognize specific, assembled capsid interfaces not present in unassembled capsid subunits.

MxB Restricts HIV-1 by Targeting the Tri-hexamer Interface of the Viral Capsid.

The human antiviral protein MxB is a restriction factor that fights HIV infection. Previous experiments have demonstrated that MxB targets the HIV capsid, a protein shell that protects the viral genome. To make the conical-shaped capsid, HIV CA proteins are organized into a lattice composed of hexamer and pentamer building blocks, providing many interfaces for host proteins to recognize.

A de novo enzyme catalyzes a life-sustaining reaction in Escherichia coli.

Producing novel enzymes that are catalytically active in vitro and biologically functional in vivo is a key goal of synthetic biology. Here we describe Syn-F4, the first de novo protein that meets both criteria. Purified Syn-F4 hydrolyzes the siderophore ferric enterobactin, and expression of Syn-F4 allows an inviable strain of Escherichia coli to grow in iron-limited medium.

A Non-natural Protein Rescues Cells Deleted for a Key Enzyme in Central Metabolism.

An important goal of synthetic biology is to create novel proteins that provide life-sustaining functions in living organisms. Recent attempts to produce novel proteins have focused largely on rational design involving significant computational efforts. In contrast, nature does not design sequences a priori.

A protein constructed de novo enables cell growth by altering gene regulation.

Recent advances in protein design rely on rational and computational approaches to create novel sequences that fold and function. In contrast, natural systems selected functional proteins without any design a priori. In an attempt to mimic nature, we used large libraries of novel sequences and selected for functional proteins that rescue Escherichia coli cells in which a conditionally essential gene has been deleted.

Push-pull macrocycles: donor-acceptor compounds with paired linearly conjugated or cross-conjugated pathways.

Two-dimensional π-systems are of current interest in the design of functional organic molecules, exhibiting unique behavior for applications in organic electronics, single-molecule devices, and sensing. Here we describe the synthesis and characterization of "push-pull macrocycles": electron-rich and electron-poor moieties linked by a pair of (matched) conjugated bridges. We have developed a two-component macrocyclization strategy that allows these structures to be synthesized with efficiencies comparable to acyclic donor-bridge-acceptor systems.

Structures of N,N-dialkoxyamides: pyramidal anomeric amides with low amidicity.

The first X-ray structures of two anomeric N,N-dialkoxyamides (2 and 3) have been obtained, which confirm that they are highly pyramidalized at nitrogen and have long N-CO bonds, a characteristic of other anomeric amides and a consequence of drastically reduced amidicity. The crystals also demonstrate chirality at the amide nitrogen in the solid state. The structures are well-predicted by density functional calculations using N,N-dimethoxyacetamide as a model.

Synthesis and thermal decomposition of N,N-dialkoxyamides.

N,N-dialkoxyamides 1c, a virtually unstudied member of the new class of anomeric amides, amides bearing two electronegative atoms at nitrogen, have been synthesised in useful yields directly from hydroxamic esters using phenyliodine(III)bis(trifluoroacetate) (PIFA). Infrared carbonyl stretch frequencies and carbonyl (13)C NMR properties have been reported, which support strong inhibition of amide resonance in these amides. Their thermal decomposition reactions in mesitylene at 155 °C proceed by homolysis to form alkoxyamidyl and alkoxyl free radicals in preference to HERON rearrangements to esters.