title: The nucleolar RNA-binding protein B-36 is highly conserved among plants.
abstract: The nucleolar protein B-36 is an RNA-associated protein which has a number of properties in common with pre-mRNA-binding proteins (hnRNP proteins). Like the hnRNP proteins, B-36 appears to be evolutionarily conserved among various eukaryotes (protists and several animal species). The conservation of B-36 throughout the plant kingdom has been investigated using a panel of nine monoclonal antibodies previously shown to recognize a minimum of four different epitopes in Physarum B-36, the protein used to generate the monoclonal antibodies. Two of the epitopes (I and III) are widely conserved in 34 kDa proteins (presumably B-36 homologues) from the various species tested (Chlamydomonas, moss, fern, oat, onion, carrot, and bean). Using immunofluorescence localization in moss and carrot protoplasts, the cross-reacting proteins were shown to be restricted to the nucleolus, further confirming their probable homology to B-36. Epitopes I and III are also unique to the B-36 homologues as demonstrated by the failure of any other bands to cross-react. Another epitope (IV) was specifically recognized in the plant B-36 homologues but exhibited greatly reduced affinity for the monoclonal antibody relative to Physarum B-36. The remaining epitope (II), unlike the others, exhibited variable conservation in the plant B-36 homologues and, in addition, was present in several other seemingly unrelated proteins. Finally, several of the plant species exhibited two cross-reacting variants at roughly the 34 kDa position and in at least one of these cases a single monoclonal antibody was able to distinguish between the two variants, a result indicating that the variants do have bona fide structural differences.(ABSTRACT TRUNCATED AT 250 WORDS)
authors: Department of Biology, Texas A & M University, College Station 77843.
authors: M J
authors: MJ
authors: Guiltinan
authors: M E
authors: ME
authors: Schelling
authors: N Z
authors: NZ
authors: Ehtesham
authors: J C
authors: JC
authors: Thomas
authors: M E
authors: ME
authors: Christensen
mesh_terms: D002352:Carrier Proteins / Q000378:metabolism*; D000939:Epitopes; D009687:Nuclear Proteins / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D016601:RNA-Binding Proteins
chemical_list: D002352:Carrier Proteins; D000939:Epitopes; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins