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N-terminal residues of plasmatocyte-spreading peptide possess specific determinants required for biological activity. J Biol Chem 2001 Oct 05;276(40):37431-5



Pubmed ID




Scopus ID

2-s2.0-0035813156   23 Citations


Plasmatocyte-spreading peptide (PSP) is a 23-amino acid cytokine that activates a class of insect immune cells called plasmatocytes. The tertiary structure of PSP consists of an unstructured N terminus (residues 1-6) and a well structured core (residues 7-23). A prior study indicated that deletion of the N terminus from PSP eliminated all biological activity. Alanine substitution of the first three residues (Glu(1)-Asn(2)-Phe(3)) further indicated that only replacement of Phe(3) resulted in a loss of activity equal to the N-terminal deletion mutant. Here, we characterized structural determinants of the N terminus. Adding a hydroxyl group to the aromatic ring of Phe(3) (making a Tyr) greatly reduced activity, whereas the addition of a fluorine (p-fluoro) did not. Substitutions that changed the chirality or replaced the aromatic ring of Phe(3) with a branched aliphatic chain (making a Val) also greatly decreased activity. The addition of a methylene group to Val (making a Leu) partially restored activity, whereas the removal of a methylene group from Phe (phenyl-Gly) eliminated all activity. These results indicated that a branched carbon chain with a methylene spacer at the third residue is the minimal structural motif required for activity. The deletion of Glu(1) also eliminated activity. Additional experiments identified the charged N-terminal amine and backbone of Glu(1) as key determinants for activity.

Author List

Clark KD, Volkman BF, Thoetkiattikul H, Hayakawa Y, Strand MR


Brian F. Volkman PhD Professor in the Biochemistry department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Glutamic Acid
Intercellular Signaling Peptides and Proteins
Molecular Sequence Data
Protein Structure, Tertiary
jenkins-FCD Prod-444 eb4ebd1a08581aba961d3befd3b851a3c3ec6b46