Highlights d BsYetJ mediates Ca 2+ flux from the ER in permeabilized mammalian cells d The Ca 2+ -binding activity is sensitive to protons and other cations d The Asp171-Asp195 dyad controls pore opening and pHdependent Ca 2+ binding d Protonation of Asp171 leads to an open-state structure

Micro-sized polyimide well-mounts for the manipulation of microcrystals and a data-assembly method for rotation data sets from many microcrystals are described.

De novo structural evaluation of native biomolecules from single-wavelength anomalous diffraction (SAD) is a challenge because of the weakness of the anomalous scattering. The anomalous scattering from relevant native elements – primarily sulfur in proteins and phosphorus in nucleic acids – increases as the X-ray energy decreases toward their K-edge transitions. Thus, measurements at a lowered X-ray energy are promising for making native SAD routine and robust. For microcrystals with sizes less than 10 µm, native-SAD phasing at synchrotron microdiffraction beamlines is even more challenging because of difficulties in sample manipulation, diffraction data collection and data analysis. Native-SAD analysis from microcrystals by using X-ray free-electron lasers has been demonstrated but has required use of thousands of thousands of microcrystals to achieve the necessary accuracy. Here it is shown that by exploitation of anomalous microdiffraction signals obtained at 5 keV, by the use of polyimide wellmounts, and by an iterative crystal and frame-rejection method, microcrystal native-SAD phasing is possible from as few as about 1 200 crystals. Our results show the utility of low-energy native-SAD phasing with microcrystals at synchrotron microdiffraction beamlines.

No abstract

The recent developments at microdiffraction X-ray beamlines are making microcrystals of macromolecules appealing subjects for routine structural analysis. Microcrystal diffraction data collected at synchrotron microdiffraction beamlines may be radiation damaged with incomplete data per microcrystal and with unit-cell variations. A multi-stage data assembly method has previously been designed for microcrystal synchrotron crystallography. Here the strategy has been implemented as a Python program for microcrystal data assembly (PyMDA). PyMDA optimizes microcrystal data quality including weak anomalous signals through iterative crystal and frame rejections. Beyond microcrystals, PyMDA may be applicable for assembling data sets from larger crystals for improved data quality.

Alkane monooxygenase (AlkB) is a widely occurring integral membrane metalloenzyme that catalyzes the initial step in the functionalization of recalcitrant alkanes with high terminal selectivity. AlkB enables diverse microorganisms to use alkanes as their sole carbon and energy source. Here we present the 48.6-kDa cryo‐electron microscopy structure of a natural fusion from Fontimonas thermophila between AlkB and its electron donor AlkG at 2.76 Å resolution. The AlkB portion contains six transmembrane helices with an alkane entry tunnel within its transmembrane domain. A dodecane substrate is oriented by hydrophobic tunnel-lining residues to present a terminal C–H bond toward a diiron active site. AlkG, an [Fe–4S] rubredoxin, docks via electrostatic interactions and sequentially transfers electrons to the diiron center. The archetypal structural complex presented reveals the basis for terminal C–H selectivity and functionalization within this broadly distributed evolutionary class of enzymes.

Edited by A. Berghuis, McGill University, CanadaKeywords: HER2-overexpressing cancer; humanized antibody; EGFR family; cell signaling; crystal structure.PDB reference: HuA21-scFv in complex with the extracellular domain of HER2, 6j71Supporting information: this article has supporting information at journals.iucr.org/d

With the recent development of microcrystal handling, synchrotron microdiffraction beamline instrumentation and data analysis, microcrystal crystallography with crystal sizes of sub-10 microns is appealing at synchrotrons. However, challenges remain in sample manipulation and data assembly for robust microcrystal synchrotron crystallography. Here we describe the development of micro-sized polyimide wellmounts for manipulation of microcrystals of a few microns and the implementation of a robust data analysis method for assembly of rotational microdiffraction datasets from many microcrystals. By progressively processing single-crystal datasets, by using a reference dataset, and by using iterative crystal and frame rejection, our data assembly procedure is quite robust. By combining these strategies, our method provides an attractive route for optimized microcrystal crystallography experiments at synchrotrons. Beyond this, our data assembly strategy may work equally well for microdiffraction from larger crystals.