Worm Breeder's Gazette 14(1): 85 (October 1, 1995)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Dept Biology, McGill University H3A 1B1 PQ Canada
Just downstream of the unc-24 gene on IV is a gene with profound similarity to vertebrate and invertebrate ADP-ribosylation factors, as revealed by our genomic DNA sequencing. Two other such genes have previously been reported (Murtagh et al. WM 91), called arf-1 III and arf-2 II. We propose naming the gene downstream of unc-24 arf-3. ARF proteins are N-myristoylated GTPases which move from the cytosol to the membrane upon GTP binding, and are involved in vesicular budding in intra-Golgi and ER - Golgi transport. ARF proteins also activate an isoform of phospholipase D, and their crystal structure is known. They were originally named for their ability to act as cofactors in the ADP-ribosylation of Gsa by cholera toxin, an activity whose relationship to the foregoing is not well understood. There is another family of proteins very similar to ARF proteins, but which lack the ability to stimulate ADP ribosylation by cholera toxin and have little effect on phospholipase D, and these have been dubbed ARL proteins, for ARF-like. Within the ARF family, three subtypes have been distinguished on the basis of similarity, namely classes I, II and III. ARLs appear to be a little more diverse, with at least 4 subtypes. ARFs are more similar to each other (80-97% identity) than ARLs are to each other (30-75% identity) and there is even less similarity across groups (35-55% identity). A search of the emerging genomic DNA sequence of chromosomes II, III and X reveals 4 new ARLs, as defined by sequence similarity. However, this analysis also suggests that arf-2 (Murtagh et al. WM 91) is, in fact, an ARL (most closely related to ARL2), not an ARF. That is, there are 2 ARFs (arf-1 and arf-3) and 5 ARLs (arf-2, arl-1 III (C38D4.8), arl-2 III (ZK632.8), arl-3 II (F54C9; like ARL1) and arl-4 II (ZK1320)). By similarity, arf-1 is class I, and arf-3 is class II. Therefore arf-2 has been renamed arl-5 (J. Hodgkin, pc).