Sperm flagella of highly divergent eukaryotic species share an architectural plan. Despite their ostensible ultrastructural similarities, mammalian sperm flagella beat with an asymmetric waveform, in contrast to the symmetrical beats of other eukaryotic flagella. Structural findings elucidate the molecular basis for this evolutionary divergence.

Recent studies offer new insight on the mechanisms of IP6-mediated HIV-1 capsid assembly. The immature Gag lattice enables enrichment of IP6 into virions, aiding capsid maturation. Structures of capsid protein (CA) assemblies reveal motifs serving as switches modulating the conformations of CA pentamers/hexamers and affect co-factor accessibility.

The RNA methyltransferase (MTase) METTL1 catalyzes N⁷-methylguanosine (m⁷G) modification at position 46 in human transfer RNAs (tRNAs). Its dysregulation drives tumorigenesis in many cancer types. Two papers now reveal the structural basis of this tRNA maturation event.

Fluorine nuclear magnetic resonance spectroscopy of the stimulatory heterotrimeric G protein reveals a conformational landscape shaped by interactions with nucleotides, the lipid bilayer and a G-protein-coupled receptor.

Here, using cryo-EM and biochemical methods, the authors demonstrate that second messenger (p)ppGpp regulates the bacterial RNA polymerase by binding to a site that is functionally relevant during transcriptional elongation but not initiation. Moreover, they demonstrate that binding to that site bears functional implications for nucleotide excision DNA repair and genome stability.

Alkane monooxygenase (AlkB) enables diverse microorganisms to hydrolyze alkanes as their sole carbon and energy source. Liu and colleagues reveal how AlkB orients an alkane to its active site and performs a selective terminal C–H bond hydroxylation.

Gabapentinoid drugs are widely used for pain, epilepsy and mental disorders. Chen et al. report the structure of a gabapentin-bound brain and heart calcium channel, revealing the gabapentin binding site and isoform-selective binding determinants.

Using atomic force microscopy, Pan et al. show that cyclic nucleotide-gated ion channel SthK, which can be differentially activated by cAMP and cGMP, binds both cyclic nucleotides but only cAMP can access a deep-bound state that could be essential for cAMP-dependent channel activation.

Tsirigotaki et al. unveil how adipokine Leptin induces trimerization of the Leptin receptor to form a cytokine-receptor assembly critical to body weight regulation, immunity, fertility and cancer.