Recombinant human Ribitol 5-phosphate transferase FKRP (EC 2.7.8.-), also known as Fukutin-related protein, is a high-quality fragment (residues 30-495) designed for structural and biochemical studies. This soluble and stable protein unit enables researchers to investigate the enzyme's critical role in glycosylation pathways essential for muscle integrity.

FKRP catalyzes the transfer of ribitol 5-phosphate from CDP-L-ribitol to the phosphorylated O-mannosyl trisaccharide on alpha-dystroglycan, forming the ribose 5-phosphate tandem repeat that links the carbohydrate structure to the ligand-binding moiety. This step is vital for functional glycosylation of alpha-dystroglycan, which is crucial for maintaining muscle cell membrane stability. The full-length protein localizes primarily to the Golgi apparatus membrane as a single-pass type II membrane protein, with additional reported localizations including the rough endoplasmic reticulum, cytoplasm, and sarcolemma. Mutations in FKRP are associated with severe clinical phenotypes, often due to endoplasmic reticulum retention of dysfunctional variants, highlighting its importance in muscular dystrophy research.