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Updated: Aug 11, 2026

Comparing the Affinity of GTPase-binding Proteins using Competition Assays
Published on: October 8, 2015
Biochemical characterization of Alsin, a Rab5 and Rac1 guanine nucleotide exchange factor
Abstract:
Alsin is the gene product mutated in three juvenile-onset neurodegenerative disorders including amyotrophic lateral sclerosis 2 (ALS2). Sequence motif searches within Alsin predict the presence of Vps9, DH, and PH domains, implying that Alsin may function as a guanine nucleotide exchange factor (GEF) for Rab5 and a member of the Rho GTPase family. Procedures are presented in this chapter for the expression, purification, and biochemical characterization of the individual GEF domains of Alsin. A fractionation method is also described for the determination of Alsin's subcellular distribution. The presence of both Rac1 and Rab5 GEF activities makes Alsin a unique dual exchange factor that may couple endocytosis (via Rab5 activation) to cytoskeletal modulation (via Rac1 activation).
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