Business science and evidence-based decision making

Space supervision and guidance of eruption in management of lower transitional crowding: A non-extraction approach

Authors' response

The management of palatally displaced maxillary canines: Considerations and challenges

Prevalence of gingival recession after orthodontic tooth movements.

Self-ligation: A clinician's point of view

Authors' response

Sky blue or murky waters: The diagnostic utility of methylene blue

Unicystic ameloblastoma: a case of mistaken identity

Resuscitation highlights in 2011

Interactions between the transmembrane domains of phospholamban (PLB) and the cardiac Ca2+ pump (SERCA2a) have been investigated by chemical cross-linking. Specifically, C-terminal, transmembrane residues 45-52 of PLB were individually mutated to Cys, then cross-linked to V89C in the M2 helix of SERCA2a with the thiol-specific cross-linking reagents Cu2+-phenanthroline, dibromobimane, and bismaleimidohexane. V49C-, M50C-, and L52C-PLB all cross-linked strongly to V89C-SERCA2a, coupling to 70-100% of SERCA2a molecules. Residues 45-48 and 51 of PLB also cross-linked to V89C of SERCA2a, but more weakly. Evidence for the mechanism of PLB regulation of SERCA2a was provided by the conformational dependence of cross-linking. In particular, the required absence of Ca2+ for cross-linking implicated the E2 conformation of SERCA2a, and its enhancement by ATP confirmed E2 x ATP as the conformation with the highest affinity for PLB. In contrast, E2 phosphorylated with inorganic phosphate (E2P) and E2 inhibited by thapsigargin (E2 x TG) both failed to cross-link to PLB. These results with transmembrane PLB residues are completely consistent with cytoplasmic PLB residues studied previously, suggesting that the dissociation of PLB from the Ca2+ pump is complete, not partial, when the pump binds Ca2+ (E1 x Ca2) or adopts the E2P or E2 x TG conformations. V49C of PLB cross-linked to 100% of SERCA2a molecules, suggesting that this residue might have functional importance for regulation. Indeed, we found that mutation of Val49 to smaller side-chained residues V49A or V49G augmented PLB inhibition, whereas mutation to the larger hydrophobic residue, V49L, prevented PLB inhibition. A model for the interaction of PLB with SERCA2a is presented, showing that Val49 fits into a constriction at the lumenal end of the M2 helix of SERCA, possibly controlling access of PLB to its binding site on SERCA.

We have reconstituted human mitochondrial transcription in vitro on DNA oligonucleotide templates representing the light strand and heavy strand-1 promoters using protein components (RNA polymerase and transcription factors A and B2) isolated from Escherichia coli. We show that 1 eq of each transcription factor and polymerase relative to the promoter is required to assemble a functional initiation complex. The light strand promoter is at least 2-fold more efficient than the heavy strand-1 promoter, but this difference cannot be explained solely by the differences in the interaction of the transcription machinery with the different promoters. In both cases, the rate-limiting step for production of the first phosphodiester bond is open complex formation. Open complex formation requires both transcription factors; however, steps immediately thereafter only require transcription factor B2. The concentration of nucleotide required for production of the first dinucleotide product is substantially higher than that required for subsequent cycles of nucleotide addition. In vitro, promoter-specific differences in post-initiation control of transcription exist, as well as a second rate-limiting step that controls conversion of the transcription initiation complex into a transcription elongation complex. Rate-limiting steps of the biochemical pathways are often those that are targeted for regulation. Like the more complex multisubunit transcription systems, multiple steps may exist for control of transcription in human mitochondria. The tools and mechanistic framework presented here will facilitate not only the discovery of mechanisms regulating human mitochondrial transcription but also interrogation of the structure, function, and mechanism of the complexes that are regulated during human mitochondrial transcription.

Electrocardiographic features of patients with COVID-19: One year of unexpected manifestations

Impaired Autophagy Triggers Chronic Pancreatitis: Lessons From Pancreas-Specific Atg5 Knockout Mice

Miniscrews and molar block anchorage reinforcement.

Central corneal thickness in children—does it help or hinder our evaluation of eyes at risk for glaucoma?