title: A rab-related GTP-binding protein in Schistosoma mansoni.
abstract: Schistosomiasis is a parasitic disease initiated by the deposition of eggs in host tissues by the blood fluke Schistosoma. A gene encoding a low-molecular weight GTP-binding protein (LMWGP) was cloned from Schistosoma mansoni using a polymerase chain reaction (PCR)-based strategy. The gene was termed smrab (Schistosoma mansoni rab-related protein). Northern blot analysis hybridizes smrab cDNA with a 1.5-kb band of mRNA; this mRNA is abundantly expressed in male schistosomes, while only slightly in females. The deduced amino acid sequence of smrab shares ca. 70% homology with that of several rab-related LMWGPs. Smrab terminates in a CCXXX motif, which is one of several signals for post-translational isoprenoid modification by geranylgeranyl protein transferase (GGPT) type II. A GGPT assay with in vitro translation product confirms that smrab is geranylgeranylated. Recombinant expression of smrab in the pET3a expression vector yields insoluble protein which migrates as a 23-kDa band on SDS-PAGE. N-terminal sequence information of the recombinant protein matches the predicted amino acid sequence of smrab. GTP-binding analysis indicates that the recombinant protein binds GTP. Therefore, smrab meets the criteria recently established for acceptance into the ras superfamily of GTP-binding proteins (Kahn, R.A., Der, C.J. and Bokoch, G.M. (1992) The ras superfamily of GTP-binding proteins: guidelines on nomenclature. FASEB J. 6, 2512-2513, Ref. [21]).
authors.affiliation: Department of Pharmacology and Toxicology, Michigan State University, East Lansing 48824-1317, USA.
authors.forename: I K
authors.initials: IK
authors.lastname: Loeffler
authors.forename: J L
authors.initials: JL
authors.lastname: Bennett
mesh_terms: D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence; D005260:Female; D019204:GTP-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D015870:Gene Expression; D017238:Genes, Helminth; D015801:Helminth Proteins; D008297:Male; D008969:Molecular Sequence Data; D010058:Oviposition; D016133:Polymerase Chain Reaction; D017368:Protein Prenylation; D012323:RNA Processing, Post-Transcriptional; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D012550:Schistosoma mansoni / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012727:Sex Characteristics; D014166:Transferases / Q000378:metabolism; D020691:rab GTP-Binding Proteins
chemical_list: D015801:Helminth Proteins; D011994:Recombinant Proteins; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C083291:geranylgeranyltransferase type-I; C104402:rab-related GTP-binding protein, Schistosoma mansoni; D019204:GTP-Binding Proteins; D020691:rab GTP-Binding Proteins