Worm Breeder's Gazette 13(1): 52 (October 1, 1993)

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.

A C. elegans homolog of gamma-adaptin, a clathrin associated protein.

Junho Lee, Paul Sternberg

HHMI, Division of Biology, Caltech, Pasadena, CA 91125

Clathrin coated pits and vesicles are involved in intracellular protein trafficking such as endocytosis, lysosomal enzyme sorting, and retention of Golgi proteins. Clathrin coated vesicles are composed of membrane, membrane proteins such as the receptors to be transported, clathrin, and its associated protein complex. There are at least two different classes of coated pits, one on the plasma membrane, and another on the trans-Golgi. Clathrin is a structural component common to both the coated pits, and their associated protein complexes are components that provide localization specificity to either the plasma membrane or the trans-Golgi coated pits. Each complex is composed of four different proteins: two large chains, one medium chain, and one small chain.

Mutations in unc-101 ,which we have shown to encode a medium chain of trans-Golgi associated protein complex, cause many different phenotypes, for example, uncoordinated movement, FITC staining defect, subviability, and suppression of vulvaless phenotype of a mutation in the receptor tyrosine kinase let-23 .The molecular basis of these phenotypes is not known. To understand the roles of clathrin associated protein complex, it is necessary to study the other components. For example, would elimination of a gamma-adaptin have the same phenotypes as unc-101 mutants?

A cDNA clone encoding a homolog of gamma-adaptin, a large chain of trans-Golgi associated protein complex, was isolated by A. R. Kerlavage et al (personal comm.). Using this cDNA clone, which has only the middle part of the gene, we identified additional cDNA clones. One clone contains six nucleotides on its 5' end that are identical to SL-1, indicating that this clone indeed contains a full length transcribed region. Partial sequence comparison reveals that C. elegans gamma-adaptin is 56% identical to mammalian gamma-adaptin, 31 to 33 % identical to alpha-adaptins, and only 20 % identical to ß-adaptin. In addition, we found that N-terminal half of the proteins are more homologous among these adaptins than C-terminal half. We have mapped this cDNA to the right end of the chromosome IV by hybridization to the YAC grid provided by A. Coulson.

P.S. In the process of obtaining more cDNA clones, we found that one of our cDNA clones had another species of cDNA unrelated to gamma-adaptin. In this cDNA clone, there is an EcoRI site, which is the cloning site for Barstead cDNA library, between gamma-adaptin cDNA and this second cDNA, indicating that the two species in one clone is a cloning artifact. The second cDNA is very similar to a yeast URA6 protein, an uridine-monophosphate kinase.