title: A novel Rab GTPase, Rab33B, is ubiquitously expressed and localized to the medial Golgi cisternae.
abstract: Small GTP-binding proteins of the Rab family play important roles at defined steps of vesicular transport in protein secretion and the endocytosis pathway. In mammals, more than 30 proteins belonging to the Rab family have been reported to date. We report here the molecular cloning and characterization of a novel Rab protein, Rab33B. The amino acid sequence of Rab33B shows 55.3% identity to the Rab33A protein (previously called S10), and these two proteins share unique amino acid sequences at the effector domain. The genomic organization of rab33B was the same as rab33A: it consists of two exons. Thus, these two proteins make a subclass within the Rab family. Northern blot analysis showed that rab33B is expressed ubiquitously in mouse tissues, in contrast to rab33A whose expression is restricted to the brain and the immune system. A 26 kDa protein was detected by western blotting using a Rab33B-specific monoclonal antibody. Using immunofluorescence studies, Rab33B was shown to co-localize with (alpha)-mannosidase II, a Golgi-specific marker. Immunoelectron microscopy analysis further defined the localization of Rab33B to the medial Golgi cisternae. These results suggest Rab33B plays a role in intra-Golgi transport.
authors.affiliation: Section of Bacterial Infection, Institute of Immunological Science, Hokkaido University, Sapporo, Japan.
authors.forename: J Y
authors.initials: JY
authors.lastname: Zheng
authors.forename: T
authors.initials: T
authors.lastname: Koda
authors.forename: T
authors.initials: T
authors.lastname: Fujiwara
authors.forename: M
authors.initials: M
authors.lastname: Kishi
authors.forename: Y
authors.initials: Y
authors.lastname: Ikehara
authors.forename: M
authors.initials: M
authors.lastname: Kakinuma
mesh_terms: D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary; D020558:GTP Phosphohydrolases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D006056:Golgi Apparatus / Q000201:enzymology* / Q000648:ultrastructure; D006801:Humans; D019169:Jurkat Cells / Q000737:chemistry / Q000201:enzymology* / Q000648:ultrastructure; D008361:Mannosidases / Q000032:analysis; D051379:Mice; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D043323:alpha-Mannosidase; D020691:rab GTP-Binding Proteins
chemical_list: D018076:DNA, Complementary; D008361:Mannosidases; D043323:alpha-Mannosidase; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C486397:RAB33B protein, human; C112838:Rab33B protein, mouse; D020691:rab GTP-Binding Proteins