Worm Breeder's Gazette 11(5): 28

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.

bli-4 Encodes a Protein Structurally Related to the Yeast Serine Endoprotease Kex2

Ken Peters and Ann Rose

Figure 1

bli-4 was cloned by Tc1 tagging (WBG 11 #2).  We probed staged 
specific and total RNA with a bli-4 cDNA.  In total RNA two bands are 
detected: 2.7 and 4.5 kb.  bli-4 is expressed throughout the life 
cycle, but most highly in L1 and L4/adult worms, and least in L2.
We have partially sequenced cDNAs that includes all of the coding 
region.  Searching the SWISSPROT protein database revealed similarity 
to the yeast gene Kex2 as well as two human genes, Fur and PC2, and a 
K.  lactis gene Kex1.  Kex2 encodes a 814 amino acid membrane bound 
serine endoprotease that activates by cleavage the alpha-mating factor 
and the killer toxin pro-proteins in the golgi body prior to secretion 
of these proteins (reviewed by R.  Fuller A.  Brake and J.  Thorner, 
Microbiology 273-278, 1986).  No function for PC2 or Fur has been 
determined.  We have sequence corresponding to 701 amino acids of bli-
4, including the amino and carboxy ends.  About 300 bp in a region 
representing about half of the Kex2 active site remains to be 
sequenced, shown as a gap in the figure below.  In 70 amino acids 
around the sequenced portion of the active site, bli-4 is 51% similar 
to the Kex2 gene, 55% similar to PC2, and 68% similar to Fur.Outside 
of the active site the sequence identity is not strong.  However, a 
number of structural features are conserved in all members of the Kex2 
gene family, (illustrated below).  These include a hydrophobic 
sequence at the amino terminal that functions as a leader sequence in 
Kex2 and a hydrophobic domain at the carboxy end that functions in 
Kex2 as a transmembrane domain (the latter is not present in the PC2 
sequence).  In addition, the spacing of these domains is conserved.
We probed EcoRI digested genomic DNA from seven alleles of bli-4.  
Of these seven, two alleles have rearrangements.  The Tc1 allele h1010 
contains a Tc1 element inserted in or just 3' to the active site.  
e937 has a 3 kb deletion fusing two adjacent EcoRI fragments at the 3' 
end of the gene.  We do not know if any of the coding region is 
deleted.  e937 is hypomorphic, and is only viable allele: all of the 
other alleles are early larval lethals.  These results suggest that 
the role of bli-4 in the cuticle may involve the processing of some 
cuticle components or some regulatory signal required for cuticle 
[See Figure 1]

Figure 1