Cryo-EM research in India.

To celebrate the 50th anniversary of Cell Press and the Cell special issue focusing on structural biology, we want to highlight the rapid progress of cryo-EM related research in India in this collection of Voices. We have asked structural biologists to introduce their research and the national cryo-EM facilities throughout the country.

SARS-CoV-2 variants of concern: spike protein mutational analysis and epitope for broad neutralization.

Mutations in the spike glycoproteins of SARS-CoV-2 variants of concern have independently been shown to enhance aspects of spike protein fitness. Here, we describe an antibody fragment (V ab6) that neutralizes all major variants including the recently emerged BA.1 and BA.

Three-Dimensional Visualization of Viral Structure, Entry, and Replication Underlying the Spread of SARS-CoV-2.

The global spread of SARS-CoV-2 has proceeded at an unprecedented rate. Remarkably, characterization of the virus using modern tools in structural biology has also progressed at exceptional speed. Advances in electron-based imaging techniques, combined with decades of foundational studies on related viruses, have enabled the research community to rapidly investigate structural aspects of the novel coronavirus from the level of individual viral proteins to imaging the whole virus in a native context.

SARS-CoV-2 Omicron variant: Antibody evasion and cryo-EM structure of spike protein-ACE2 complex.

The newly reported Omicron variant is poised to replace Delta as the most prevalent SARS-CoV-2 variant across the world. Cryo-EM structural analysis of the Omicron variant spike protein in complex with human ACE2 reveals new salt bridges and hydrogen bonds formed by mutated residues R493, S496 and R498 in the RBD with ACE2. These interactions appear to compensate for other Omicron mutations such as K417N known to reduce ACE2 binding affinity, resulting in similar biochemical ACE2 binding affinities for Delta and Omicron variants.

Structural analysis of receptor binding domain mutations in SARS-CoV-2 variants of concern that modulate ACE2 and antibody binding.

The recently emerged severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) Beta (B.1.351) and Gamma (P.

Cryo-electron microscopy structures of the N501Y SARS-CoV-2 spike protein in complex with ACE2 and 2 potent neutralizing antibodies.

The recently reported "UK variant" (B.1.1.

High Potency of a Bivalent Human V Domain in SARS-CoV-2 Animal Models.

Novel COVID-19 therapeutics are urgently needed. We generated a phage-displayed human antibody V domain library from which we identified a high-affinity V binder ab8. Bivalent V, V-Fc ab8, bound with high avidity to membrane-associated S glycoprotein and to mutants found in patients.

and human hexokinases share similar active sites but display distinct quaternary architectures.

Malaria is a devastating disease caused by a protozoan parasite. It affects over 300 million individuals and results in over 400 000 deaths annually, most of whom are young children under the age of five. Hexokinase, the first enzyme in glucose metabolism, plays an important role in the infection process and represents a promising target for therapeutic intervention.

βγ-Crystallination Endows a Novel Bacterial Glycoside Hydrolase 64 with Ca-Dependent Activity Modulation.

The prokaryotic βγ-crystallins are a large group of uncharacterized domains with Ca-binding motifs. We have observed that a vast number of these domains are found appended to other domains, in particular, the carbohydrate-active enzyme (CAZy) domains. To elucidate the functional significance of these prospective Ca sensors in bacteria and this widespread domain association, we have studied one typical example from , a bacterium known for its ability to produce acetone, butanol, and ethanol through fermentation of several carbohydrates.

A Transition Metal-Binding, Trimeric βγ-Crystallin from Methane-Producing Thermophilic Archaea, Methanosaeta thermophila.

βγ-Crystallins are important constituents of the vertebrate eye lens, whereas in microbes, they are prevalent as Ca-binding proteins. In archaea, βγ-crystallins are conspicuously confined to two methanogens, viz., Methanosaeta and Methanosarcina.

Microbial βγ-crystallins.

βγ-Crystallins have emerged as a superfamily of structurally homologous proteins with representatives across the domains of life. A major portion of this superfamily is constituted by members from microorganisms. This superfamily has also been recognized as a novel group of Ca(2+)-binding proteins with huge diversity.

Ca2+-binding motif of βγ-crystallins.

βγ-Crystallin-type double clamp (N/D)(N/D)XX(S/T)S motif is an established but sparsely investigated motif for Ca(2+) binding. A βγ-crystallin domain is formed of two Greek key motifs, accommodating two Ca(2+)-binding sites. βγ-Crystallins make a separate class of Ca(2+)-binding proteins (CaBP), apparently a major group of CaBP in bacteria.

Aggregation-prone near-native intermediate formation during unfolding of a structurally similar nonlenticular βγ-crystallin domain.

The folding and unfolding of structurally similar proteins belonging to a family have long been a focus of investigation of the structure-(un)folding relationship. Such studies are yet to reach a consensus about whether structurally similar domains follow common or different unfolding pathways. Members of the βγ-crystallin superfamily, which consists of structurally similar proteins with limited sequence similarity from diverse life forms spanning microbes to mammals, form an appropriate model system for exploring this relationship further.

Decoding the molecular design principles underlying Ca(2+) binding to βγ-crystallin motifs.

Numerous proteins belonging to the recently expanded βγ-crystallin superfamily bind Ca(2+) at the double-clamp N/D-N/D-X(1)-X(2)-S/T-S motif. However, there have been no attempts to understand the intricacies involving Ca(2+) binding, such as the determinants of Ca(2+)-binding affinity and their contributions to gain in stability. This work is an in-depth analysis of understanding the modes and determinants of Ca(2+) binding to βγ-crystallin motifs.