Calcium Contributes to Polarized Targeting of HIV Assembly Machinery by Regulating Complex Stability.

Polarized or precision targeting of protein complexes to their destinations is fundamental to cellular homeostasis, but the mechanism underpinning directional protein delivery is poorly understood. Here, we use the uropod targeting HIV synapse as a model system to show that the viral assembly machinery Gag is copolarized with the intracellular calcium (Ca) gradient and binds specifically with Ca. Conserved glutamic/aspartic acids flanking endosomal sorting complexes required for transport binding motifs are major Ca binding sites.

Purification of an insect juvenile hormone receptor complex enables insights into its post-translational phosphorylation.

Juvenile hormone (JH) plays vital roles in insect reproduction, development, and in many aspects of physiology. JH primarily acts at the gene-regulatory level through interaction with an intracellular receptor (JH receptor [JHR]), a ligand-activated complex of transcription factors consisting of the JH-binding protein methoprene-tolerant (MET) and its partner taiman (TAI). Initial studies indicated significance of post-transcriptional phosphorylation, subunit assembly, and nucleocytoplasmic transport of JHR in JH signaling.

Crystal structure of fungal tannase from Aspergillus niger.

Tannases are serine esterases that were first discovered in fungi more than one and half centuries ago. They catalyze the hydrolysis of the gallolyl ester bonds in gallotannins to release gallic acid, which is an important intermediate in the chemical and pharmaceutical industries. Since their discovery, fungal tannases have found wide industrial applications, although there is scarce knowledge about these enzymes at the molecular level, including their catalytic and substrate-binding sites.

The C-terminal p6 domain of the HIV-1 Pr55 precursor is required for specific binding to the genomic RNA.

The Pr55 precursor specifically selects the HIV-1 genomic RNA (gRNA) from a large excess of cellular and partially or fully spliced viral RNAs and drives the virus assembly at the plasma membrane. During these processes, the NC domain of Pr55 interacts with the gRNA, while its C-terminal p6 domain binds cellular and viral factors and orchestrates viral particle release. Gag∆p6 is a truncated form of Pr55 lacking the p6 domain usually used as a default surrogate for wild type Pr55 for in vitro analysis.