Fn2yx

Fn2yx is a hypothetical protein family consisting of small, soluble proteins found in a subset of bacterial and archaeal genomes. Members are defined by a conserved N-terminal motif and an overall length of approximately 110–140 amino acids. The designation Fn2yx originates from a project-specific code used in initial in silico analyses and has since appeared in multiple protein-annotation databases as a putative family.

Discovery and distribution: Fn2yx was first described in 2022 during large-scale computational surveys of uncharacterized proteins in environmental DNA assemblies. Homologs have been reported across diverse lineages, including extremophiles from hot springs and deep-sea sediments. In many genomes, Fn2yx genes occur in operons alongside genes linked to metal handling or RNA processing, though direct functional links remain unconfirmed.

Structure and motifs: Sequence analyses predict a compact, primarily beta-sheet fold for Fn2yx members. A conserved region at the N-terminus and a nearby cysteine/histidine-rich motif have led to speculation of a potential metal-binding site, possibly coordinating a zinc ion. No experimentally determined structures exist, and predicted transmembrane regions are not indicated, suggesting a soluble cytosolic localization.

Function and significance: The biological role of Fn2yx is uncertain. In silico evidence hints at possible involvement in metal homeostasis or RNA metabolism, but there is no confirmed experimental annotation. Due to its broad phylogenetic distribution in environmental genomes, Fn2yx serves as a useful test case for annotation pipelines and for evaluating structure-prediction methods in genomic datasets.

See also: Hypothetical proteins, protein families, metal-binding proteins.