Worm Breeder's Gazette 10(3): 108

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.

Paramyosin Phosphorylation, Part II

Lawrence A. Schriefer and Robert H. Waterston

Figure 1

In the vol.10, number 2 edition of The Wormbreeder's Gazette, we 
reported that paramyosin is phosphorylated in vitro under low salt 
conditions by an endogenous kinase in a reaction that is Ca++ 
independent.  Thin layer chromatography indicated that paramyosin 
contained phosphoserine.  Phosphate assays suggested that in vivo 
paramyosin had 1.8 moles of phosphate per mole of paramyosin.
To determine the sites of phosphorylation, in vitro phosphorylated 
paramyosin was digested by NTCB.  A 15,000 Da fragment was 
phosphorylated which corresponded to the N-terminal fragment according 
to Hiro Kagawa's sequence data.  To obtain a more precise localization,
in vitro labelled paramyosin was digested by endoproteinase-Lys-C.  2 
labelled HPLC fractions were obtained and subjected to protein 
sequencing.  One however yielded no sequence, and since the N-terminus 
of paramyosin is known to be blocked, probably by acetylation, we 
guessed that this peptide included the blocked N-terminus.  Amino acid 
composition of the peptide was determined.  The second peptide was 
sequenced with no difficulty.  This sequence and the amino acid 
composition data of the blocked peptide were compared with H.  
Kagawa's DNA sequence of the paramyosin gene, unc-15.  They appear to 
arise from, and together define the N-terminus of paramyosin.
[See Figure 1]
With three prolines, two glycines, and eight serines(*), the N-
terminal region that we have determined is decidedly not alpha-helical 
coiled-coil in structure and is substantially different then the 
remainder of C.  elegans paramyosin (Kagawa's sequence) and myosin rod 
sequences.  It would be interesting to determine what role the 
phosphorylation of the non-helical N-terminus of paramyosin plays in 
the interaction between paramyosin and other proteins in C.  elegans' 
thick filament formation and function.

Figure 1