Ribosomebound

Ribosomebound is a term used in molecular biology to describe molecules that are physically associated with ribosomes during translation, typically RNA transcripts or protein complexes. In most cells, ribosomes may be free in the cytosol or bound to membranes such as the rough endoplasmic reticulum or the outer surface of mitochondria. The term emphasizes the functional state of translation and nascent polypeptide handling.

Ribosomebound commonly refers to ribosome-bound mRNA, which forms polysomes when multiple ribosomes translate a single transcript. In eukaryotes, ribosome binding often involves initiation factors and, for secretory or membrane proteins, the signal recognition particle targets the ribosome-mRNA-nascent chain complex to the endoplasmic reticulum, where translation continues and the polypeptide enters the ER lumen or integrates into the membrane.

Techniques such as ribosome profiling, polysome fractionation, and ribosome immunoprecipitation distinguish ribosomebound transcripts from non-bound fractions, enabling study of translation efficiency and mRNA regulation. Ribosome display is a related in vitro method that uses a ribosome-bound complex of mRNA and nascent protein to select for binding properties.

Understanding ribosomebound states informs gene expression regulation, protein targeting, and co-translational folding. However, the dynamic nature of ribosome association makes it challenging to capture in fixed samples, and experimental definitions of bound can vary by organism and context.

See also: ribosome, translation, polysome, ribosome profiling, ribosome display.