Alaninerich

Alaninerich is an adjective used in biochemistry and molecular biology to describe molecules, typically proteins, that contain a higher than average proportion of the amino acid alanine (A). In protein sequences, alaninerich regions often consist of runs of alanine residues, sometimes referred to as polyalanine tracts. Researchers identify alaninerich segments using amino acid composition analyses and sequence screening, often applying a threshold for contiguous alanines.

Alanine is a small, nonpolar amino acid with a high propensity to form alpha helices. Consequently, alaninerich regions tend to contribute to alpha-helical structure within proteins. At the same time, such regions can participate in intrinsic disorder when embedded in certain sequence contexts, contributing to low-complexity domains and flexible linkers in proteins.

Biological significance: alaninerich sequences occur in diverse organisms and are sometimes enriched in transcription factors and structural proteins. Polyalanine tracts are a notable feature; variations in tract length can affect protein function, stability, and localization. In humans, expansions of polyalanine tracts in certain proteins have been linked to disease, including oculopharyngeal muscular dystrophy, which results from expansion in the polyalanine region of PABPN1, along with other polyalanine expansion disorders described in developmental and neurological conditions.

Applications and research: alaninerich polymers and polypeptides serve as model systems for studying protein folding, helix formation, and phase behavior. In biomaterials research, short alaninerich peptides are explored as building blocks for nanostructures and scaffolds due to their tendency to form stable alpha-helices and, in some cases, coiled-coil assemblies.