Calorimetric analysis of AdcR and its interactions with zinc(II) and DNA.

Zinc(II) ions play critical roles in all known life as structurally important stabilizing ions in proteins, catalytically active metals in enzymes, and signaling agents impacting physiological changes. To maintain homeostasis, the intracellular concentration of zinc(II) is strictly controlled by a family of metal-regulatory proteins in both prokaryotic and eukaryotic organisms. In S.

Individual variability in foraging success of a marine predator informs predator management.

The complexities of trophic dynamics complicate the management of predator populations. Targeted culling campaigns are one management strategy meant to control predation for the benefit of the prey population. In these campaigns, individual predators are often considered "rogue" based on visitation rates to the site of concern.

Modifications of cysteine residues in the transmembrane and cytoplasmic domains of a recombinant hemagglutinin protein prevent cross-linked multimer formation and potency loss.

Background: Recombinant hemagglutinin (rHA) is the active component in Flublok®; a trivalent influenza vaccine produced using the baculovirus expression vector system (BEVS). HA is a membrane bound homotrimer in the influenza virus envelope, and the purified rHA protein assembles into higher order rosette structures in the final formulation of the vaccine. During purification and storage of the rHA, disulfide mediated cross-linking of the trimers within the rosette occurs and results in reduced potency.

Titer on chip: new analytical tool for influenza vaccine potency determination.

Titer on Chip (Flu-ToC) is a new technique for quantification of influenza hemagglutinin (HA) concentration. In order to evaluate the potential of this new technique, a comparison of Flu-ToC to more conventional methods was conducted using recombinant HA produced in a baculovirus expression system as a test case. Samples from current vaccine strains were collected from four different steps in the manufacturing process.

Thrombopoietin receptor activation: transmembrane helix dimerization, rotation, and allosteric modulation.

We report how rotational variations in transmembrane (TM) helix interactions participate in the activity states of the thrombopoietin receptor (TpoR), a type 1 cytokine receptor that controls the production of blood platelets. We also explore the mechanism of small-molecule agonists that do not mimic the natural ligand. We show, by a combination of cysteine cross-linking, alanine-scanning mutagenesis, and computational simulations, that the TpoR TM dimerizes strongly and can adopt 3 different stable, rotationally related conformations, which may correspond to specific states of the full-length receptor (active, inactive, and partially active).

Unusual presentation of myeloid sarcoma in a case of acute promyelocytic leukemia with a cryptic PML-RARA rearrangement involving multiple sites including the atrium.

Myeloid sarcoma is an extramedullary tumor mass composed of immature myeloid cells. Myeloid sarcoma may develop de novo, concurrently with acute myeloid leukemia (AML), or at relapse. Although myeloid sarcoma can occur at any site, myeloid sarcoma involving the heart is extremely rare.

Cytogenetic and molecular characterization of a partial trisomy 2p arising from inverted duplication of 2p with terminal deletion of 2pter.

Partial trisomy 2p is typically associated with partial monosomy of another chromosomal segment and results from a balanced translocation in one of the parents. Inverted duplications with terminal deletions have been reported in an increasing number of chromosomes. Several cases initially interpreted as terminal duplications have instead been documented to represent inverted duplications with terminal deletions.

Dynamic helix interactions in transmembrane signaling.

Studying how protein transmembrane domains transmit signals across membranes is beset by unique challenges. Here, we discuss the circumstances that have led to success and reflect on what has been learned from these examples. Such efforts suggest that some of the most interesting properties of transmembrane helix interactions may be the least amenable to study by current techniques.

Toward beta-amino acid proteins: a cooperatively folded beta-peptide quaternary structure.

Folded polymers in nature are assembled from simple monomers and adopt complex folded structures through networks of stabilizing noncovalent interactions. These interactions define secondary and tertiary structure and in most cases specify a unique three-dimensional architecture. Individual secondary or tertiary structures can also associate with one another to form multi-subunit quaternary structures.

Mutations of conserved glycine residues within the membrane-spanning domain of human immunodeficiency virus type 1 gp41 can inhibit membrane fusion and incorporation of Env onto virions.

The membrane-spanning domain (MSD) of HIV-1 envelope protein (Env) has an additional glycine residue within a well-conserved putative transmembrane helix-helix interaction motif, GXXXG, and forms a G(690)G(691)XXG(694) sequence (G, glycine; X, any residues; the numbering indicates the position within the Env of an infectious molecular clone, HXB2). Different from vesicular stomatitis virus G (VSV-G), the glycine residues of the GXXXG motif of HIV-1 showed higher tolerance against mutations, and a simultaneous substitution of G690 and G694 with leucine residues only modestly decreased fusion activity and replication capacity of HIV-1. When G691 was further substituted with alanine, phenylalanine or leucine residue while G690 and G694 were substituted with leucine residues, the efficiency of membrane fusion decreased, with the decrease greatest occurring with the leucine substitution, a less severe decrease with phenylalanine, and the least severe decrease with alanine.

Invariant chain transmembrane domain trimerization: a step in MHC class II assembly.

The transmembrane (TM) domain of the major histocompatibility complex (MHC) class II-associated invariant chain (Ii) has long been implicated in both correct folding and function of the MHC class II complex. To function correctly, Ii must form a trimer, and the TM domain is one of the domains thought to stabilize the trimeric state. Specific mutations in the TM domain have been shown previously to disrupt MHC class II functions such as mature complex formation and antigen presentation, possibly due to disruption of Ii TM helix-helix interactions.

Hydrodynamic characterization of the DEAD-box RNA helicase DbpA.

The Escherichia coli DEAD-box protein A (DbpA) belongs to the highly conserved superfamily-II of nucleic acid helicases that play key roles in RNA metabolism. A central question regarding helicase activity is whether the process of coupling ATP hydrolysis to nucleic acid unwinding requires an oligomeric form of the enzyme. We have investigated the structural and functional properties of DbpA by multi-angle laser light-scattering, size-exclusion chromatography, analytical ultracentrifugation, chemical cross-linking and hydrodynamic modeling.

Membrane protein folding: beyond the two stage model.

The folding of alpha-helical membrane proteins has previously been described using the two stage model, in which the membrane insertion of independently stable alpha-helices is followed by their mutual interactions within the membrane to give higher order folding and oligomerization. Given recent advances in our understanding of membrane protein structure it has become apparent that in some cases the model may not fully represent the folding process. Here we present a three stage model which gives considerations to ligand binding, folding of extramembranous loops, insertion of peripheral domains and the formation of quaternary structure.

Helix macrodipole control of beta 3 peptide 14-helix stability in water.

beta-Peptides have attracted considerable attention by virtue of their ability to populate helical secondary structures in methanol, even in the absence of stabilizing tertiary interactions. Recent efforts in beta-peptide design have produced few beta3-peptides that form stable 14-helices in water; those that do require stabilizing intramolecular salt bridges on two of three helical faces and therefore possess limited utility as tools in biological research. Here we show that favorable interactions with the 14-helix macrodipole significantly stabilize the 14-helix in water, alleviating the need for multiple salt bridges on two of three helical faces.