RaPID hookup

March 19th, 2018 by Grant Miura

RaPID hookup

RaPID hookup, Published online: 19 March 2018; doi:10.1038/s41589-018-0030-7

RaPID hookup

An optically controlled probe identifies lipid-gating fenestrations within the TRPC3 channel

March 19th, 2018 by Michaela Lichtenegger

An optically controlled probe identifies lipid-gating fenestrations within the TRPC3 channel

An optically controlled probe identifies lipid-gating fenestrations within the TRPC3 channel, Published online: 19 March 2018; doi:10.1038/s41589-018-0015-6

A photoswitchable diacylglycerol enabled a screen that found critical TRPC3 lipid-sensing residues and identified a lateral fenestration in the pore domain that allows lipids to protrude into the permeation pathway to control channel gating.
  • Posted in Nat Chem Biol, Publications
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Specialized splicing

March 19th, 2018 by Caitlin Deane

Specialized splicing

Specialized splicing, Published online: 19 March 2018; doi:10.1038/s41589-018-0027-2

Specialized splicing

Whole-organism phenotypic screening for anti-infectives promoting host health

March 19th, 2018 by Anne E. Clatworthy

Whole-organism phenotypic screening for anti-infectives promoting host health

Whole-organism phenotypic screening for anti-infectives promoting host health, Published online: 19 March 2018; doi:10.1038/s41589-018-0018-3

Targeting the host during antibiotic discovery efforts is a viable strategy, and the approach has benefited from phenotypic screening of model organisms such as worms, zebrafish, and mice.
  • Posted in Nat Chem Biol, Publications
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Structural basis for backbone N-methylation by an interrupted adenylation domain

March 19th, 2018 by Shogo Mori

Structural basis for backbone N-methylation by an interrupted adenylation domain

Structural basis for backbone N-methylation by an interrupted adenylation domain, Published online: 19 March 2018; doi:10.1038/s41589-018-0014-7

The crystal structure of a methyltransferase domain embedded within an interrupted adenylation domain provides insight into how a nonribosomal peptide synthetase N-methylates amino acid precursors for their incorporation into the peptide product.
  • Posted in Nat Chem Biol, Publications
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Mix and match

March 19th, 2018 by Karin Kuehnel

Mix and match

Mix and match, Published online: 19 March 2018; doi:10.1038/s41589-018-0028-1

Mix and match

Discovery of enzymes for toluene synthesis from anoxic microbial communities

March 19th, 2018 by Harry R. Beller

Discovery of enzymes for toluene synthesis from anoxic microbial communities

Discovery of enzymes for toluene synthesis from anoxic microbial communities, Published online: 19 March 2018; doi:10.1038/s41589-018-0017-4

The source of biological toluene production in diverse anoxic microbial communities is a glycyl radical enzyme that catalyzes phenylacetate decarboxylation (PhdB), and its cognate activating radical S-adenosylmethionine enzyme (PhdA).
  • Posted in Nat Chem Biol, Publications
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Cryo-EM structure of a mammalian RNA polymerase II elongation complex inhibited by {alpha}-amanitin [Protein Structure and Folding]

March 17th, 2018 by Xiangyang Liu, Lucas Farnung, Christoph Wigge, Patrick Cramer

RNA polymerase II (Pol II) is the central enzyme that transcribes eukaryotic protein-coding genes to produce mRNA. The mushroom toxin α-amanitin binds Pol II and inhibits transcription at the step of RNA chain elongation. Pol II from yeast binds α-amanitin with micromolar affinity, whereas metazoan Pol II enzymes exhibit nanomolar affinities. Here, we present the high-resolution cryo-EM structure of α-amanitin bound to and inhibited by its natural target, the mammalian Pol II elongation complex. The structure revealed that the toxin is located in a pocket previously identified in yeast Pol II, but forms additional contacts with metazoan-specific residues, which explain why its affinity to mammalian Pol II is ~3000 times higher than for yeast Pol II. Our work provides the structural basis for the inhibition of mammalian Pol II by the natural toxin α-amanitin and highlights that cryo-EM is well suited to studying interactions of a small molecule with its macromolecular target.

The major facilitator transporter Str3 is required for low-affinity heme acquisition in Schizosaccharomyces pombe [Microbiology]

March 16th, 2018 by Vincent Normant, Thierry Mourer, Simon Labbe

In the fission yeast Schizosaccharomyces pombe, acquisition of exogenous heme is largely mediated by the cell membrane-associated Shu1. Here, we report that Str3, a member of the major facilitator superfamily of transporters promotes cellular heme import. Using a strain that cannot synthesize heme de novo (hem1Δ) and lacks Shu1, we found that the heme-dependent growth deficit of this strain is rescued by hemin supplementation in the presence of Str3. Microscopic analyses of a hem1Δ shu1Δ str3Δ mutant strain in the presence of the heme analog zinc mesoporphyrin IX (ZnMP) revealed that ZnMP fails to accumulate within the mutant cells. In contrast, Str3-expressing hem1Δ shu1Δ cells could take up ZnMP at a 10-μM concentration. The yeast Saccharomyces cerevisiae cannot efficiently transport exogenously supplied hemin. However, heterologous expression of Str3 from S. pombe in S. cerevisiae resulted in ZnMP accumulation within S. cerevisiae cells. Moreover, hemin-agarose pulldown assays revealed that Str3 binds hemin. In contrast, a Str3 mutant in which Tyr and Ser residues of two putative heme-binding motifs (530Y-X3-Y534 and 552S-X4-Y557) had been replaced with alanines exhibited a loss of affinity for hemin. Furthermore, this Str3 mutant failed to rescue the heme-dependent growth deficit of a hem1Δ shu1Δ str3Δ strain. Further analysis by absorbance spectroscopy disclosed that a predicted extracellular loop region in Str3 containing the two putative heme-binding motifs interacts with hemin, with a KD of 6.6 μM. Taken together, these results indicate that Str3 is a second cell-surface membrane protein for acquisition of exogenous heme in S. pombe.

Relationship of Sequence and Phase Separation in Protein Low-Complexity Regions

March 16th, 2018 by Erik W. Martin and Tanja Mittag

TOC Graphic

Biochemistry
DOI: 10.1021/acs.biochem.8b00008