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.

arf, arf, arf! A dogged tale.

Tom Barnes, Siegfried Hekimi

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).