title: Defective Guanine Nucleotide Exchange in the Elongation Factor-like 1 (EFL1) GTPase by Mutations in the Shwachman-Diamond Syndrome Protein.
abstract: Ribosome biogenesis is orchestrated by the action of several accessory factors that provide time and directionality to the process. One such accessory factor is the GTPase EFL1 involved in the cytoplasmic maturation of the ribosomal 60S subunit. EFL1 and SBDS, the protein mutated in the Shwachman-Diamond syndrome (SBDS), release the anti-association factor eIF6 from the surface of the ribosomal subunit 60S. Here we report a kinetic analysis of fluorescent guanine nucleotides binding to EFL1 alone and in the presence of SBDS using fluorescence stopped-flow spectroscopy. Binding kinetics of EFL1 to both GDP and GTP suggests a two-step mechanism with an initial binding event followed by a conformational change of the complex. Furthermore, the same behavior was observed in the presence of the SBDS protein irrespective of the guanine nucleotide evaluated. The affinity of EFL1 for GTP is 10-fold lower than that calculated for GDP. Association of EFL1 to SBDS did not modify the affinity for GTP but dramatically decreased that for GDP by increasing the dissociation rate of the nucleotide. Thus, SBDS acts as a guanine nucleotide exchange factor (GEF) for EFL1 promoting its activation by the release of GDP. Finally, fluorescence anisotropy measurements showed that the S143L mutation present in the Shwachman-Diamond syndrome altered a surface epitope for EFL1 and largely decreased the affinity for it. These results suggest that loss of interaction between these proteins due to mutations in the disease consequently prevents the nucleotide exchange regulation the SBDS exerts on EFL1.
authors.affiliation: Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México.
authors.forename: Adrián
authors.initials: A
authors.lastname: García-Márquez
authors.affiliation: Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México.
authors.forename: Abril
authors.initials: A
authors.lastname: Gijsbers
authors.affiliation: Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México.
authors.forename: Eugenio
authors.initials: E
authors.lastname: de la Mora
authors.affiliation: Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, c.p 04510, México D.F., México. Electronic address: nuriasp@unam.mx.
authors.forename: Nuria
authors.initials: N
authors.lastname: Sánchez-Puig
mesh_terms: D001855:Bone Marrow Diseases / Q000235:genetics / Q000378:metabolism; D010188:Exocrine Pancreatic Insufficiency / Q000235:genetics / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008068:Lipomatosis / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010445:Peptide Elongation Factors; D011485:Protein Binding; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D017415:Ribonucleoprotein, U5 Small Nuclear; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism; D000081003:Shwachman-Diamond Syndrome
chemical_list: C000599132:EFL1 protein, human; D006150:Guanine Nucleotides; D010445:Peptide Elongation Factors; D011506:Proteins; D017415:Ribonucleoprotein, U5 Small Nuclear; C470521:SBDS protein, human; D020558:GTP Phosphohydrolases
keywords: EFL1; GTPase; Shwachman-Diamond syndrome protein; fluorescence anisotropy; fluorescence resonance energy transfer (FRET); guanine nucleotide exchange factor (GEF); guanine nucleotides; ribosome assembly