A protein with a molecular weight of 17K, immunoreactive with the S-1B2 ant
ibody, has been isolated from hemocytes of Halocynthia roretzi. Its amino a
cid sequence has been determined by sequential Edman degradation analysis o
f peptide fragments derived from proteolytic fragmentation. The 17K protein
is a single chain protein consisting of 151 amino acids with an acylated N
-terminal serine. A comparison of the amino acid sequence of H. roretzi 17K
protein with those of other proteins reveals that the 17K protein is Cu,Zn
-SOD. The protein was found to have a KCN-inhibited SOD activity. Cu,Zn-SOD
has been purified from H. roretzi plasma. The molecular weight is 17K and
the activity is inhibited with KCN and diethyldithiocarbamate. It has been
demonstrated that it can enhance phagocytosis by H. roretzi hemocytes. Thus
, plasma Cu,Zn-SOD plays a role in H. roretzi as a defense molecule. (C) 19
99 Elsevier Science Inc. All rights reserved.