title: Guanine nucleotide exchange in the ribosomal GTPase EFL1 is modulated by the protein mutated in the Shwachman-Diamond syndrome.
abstract: Ribosome biogenesis in eukaryotes is a complex process that requires the participation of several accessory proteins that are not part of the mature particle. Efl1 is a yeast GTPase required for the cytoplasmic maturation of the 60S ribosomal subunit. Together with Sdo1, the yeast ortholog of the protein mutated in the Shwachman-Diamond Syndrome (SBDS), Efl1 releases the anti-association factor Tif6 from the surface of the 60S subunit allowing the assembly of mature ribosomes. We characterized the structural content and folding stability of the Saccharomyces cerevisiae and human EFL1 GTPases, as well as their enzymatic properties alone and in the presence of Sdo1 and SBDS, respectively. The human and S. cerevisiae EFL1 GTPases are composed of a mixture of α-helices and β-sheets. Despite being orthologs, the yeast protein elicited a non-two state thermal unfolding behavior while the human EFL1 was highly resistant to thermal denaturation. Steady-state kinetic analyses indicated slow GTP hydrolysis for both EFL1 GTPases, with kcat values of 0.4 and 0.3min(-1) and Km for GTP of 110 and 180μM respectively. In the presence of the effector proteins, their kcat values remained unaltered while the Km decreased twofold suggesting that Sdo1 and SBDS act as nucleotide exchange factors.
authors.affiliation: Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Av. Universidad 3000, Ciudad Universitaria, C.P. 04510, México, D.F., Mexico.
authors.forename: Abril
authors.initials: A
authors.lastname: Gijsbers
authors.forename: Adrián
authors.initials: A
authors.lastname: García-Márquez
authors.forename: Axel
authors.initials: A
authors.lastname: Luviano
authors.forename: Nuria
authors.initials: N
authors.lastname: Sánchez-Puig
mesh_terms: D001855:Bone Marrow Diseases / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D004795:Enzyme Stability / Q000235:genetics; D010188:Exocrine Pancreatic Insufficiency / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008068:Lipomatosis / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D058767:Protein Unfolding; D011506:Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000081003:Shwachman-Diamond Syndrome; D013816:Thermodynamics
chemical_list: D011506:Proteins; D012269:Ribosomal Proteins; C470521:SBDS protein, human; D029701:Saccharomyces cerevisiae Proteins; C520002:Sdo1 protein, S cerevisiae; D020558:GTP Phosphohydrolases; C520003:RIA1 protein, S cerevisiae
keywords: EFL1; GTPase; Guanine exchange factor; Shwachman–Diamond Syndrome protein