title: Mon2  is a negative regulator of the monomeric G protein, Arl1.
abstract: Using site-directed mutants of ARL1 predicted to alter nucleotide binding, we examined phenotypes associated with the loss of ARL1 , including effects on membrane traffic and K (+)  homeostasis. The GTP-restricted allele, ARL[Q72L] , complemented the membrane traffic phenotype (CPY secretion), but not the K (+)  homeostasis phenotypes (sensitivity to hygromycin B, steady-state levels of K (+)  , and accumulation of (86)  Rb (+)  ), while the XTP-restricted mutant, ARL1[D130N] , complemented the ion phenotypes, but not the membrane traffic phenotype. A GDP-restricted allele, ARL1[T32N] , did not effectively complement either phenotype. These results are consistent with a model in which Arl1 has three different conformations in vivo. We also explored the relationship between ARL1 and MON2 using the synthetic lethal phenotype exhibited by these two genes and demonstrated that MON2 is a negative regulator of the GTP-restricted allele of ARL1 , ARL1[Q72L] . Finally, we constructed several new alleles predicted to alter binding of Arl1 to the sole GRIP domain containing protein in yeast, Imh1, and found that ARL1[F52G] and ARL1[Y82G] were unable to complement the loss of ARL1 with respect to either the membrane traffic or K (+)  homeostasis phenotypes. Our study expands understanding of the roles of Arl1 in vivo.
authors.affiliation: Department of Biology, Georgetown University, Washington, DC 20057-1229, USA.
authors.forename: Cara Marie A
authors.initials: CM
authors.lastname: Manlandro
authors.forename: Vikram R
authors.initials: VR
authors.lastname: Palanivel
authors.forename: Emily B
authors.initials: EB
authors.lastname: Schorr
authors.forename: Nino
authors.initials: N
authors.lastname: Mihatov
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Antony
authors.forename: Anne G
authors.initials: AG
authors.lastname: Rosenwald
mesh_terms: D019943:Amino Acid Substitution; D015966:Gene Expression Regulation, Fungal; D005816:Genetic Complementation Test; D008954:Models, Biological; D020559:Monomeric GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000096:biosynthesis / Q000235:genetics; D020125:Mutation, Missense; D011188:Potassium / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*
chemical_list: C507257:MON2 protein, S cerevisiae; D050505:Mutant Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C487039:ARL1 protein, S cerevisiae; D020559:Monomeric GTP-Binding Proteins; D011188:Potassium