Structure and biosynthesis of Lyt-1

Area of Science:

• Immunogenetics
• Molecular immunology
• Cell surface antigens

Background:

• Lyt-1 is a cell surface glycoprotein found on thymocytes.
• The genetic locus controlling Lyt-1 alloantigens is located on chromosome 19.
• Understanding the structural basis of Lyt-1 allo-specificity is crucial for immunological studies.

Purpose of the Study:

• To determine if the Lyt-1 locus encodes the protein-structural gene for Lyt-1.
• To investigate the contribution of protein versus carbohydrate moieties to Lyt-1 allo-specificity.

Main Methods:

• Two-dimensional chymotryptic peptide mapping of Lyt-1.1 and Lyt-1.2 from 125I-labeled thymocytes and solubilized membrane fragments.
• Precipitation of 35S-cysteine-labeled thymocyte proteins (including tunicamycin-treated cells) using Lyt-1 alloantibody.

Main Results:

• Peptide maps of Lyt-1.1 and Lyt-1.2 from intact thymocytes showed no significant differences.
• Characteristic differences were observed in peptide maps from solubilized membrane fragments.
• Lyt-1 alloantibody precipitated an intermediate 62K form and a 60K form (from tunicamycin-treated cells), indicating protein involvement.

Conclusions:

• The Lyt-1 locus on chromosome 19 includes the protein-structural gene for Lyt-1.
• Allo-specificity of the Lyt-1 glycoprotein (67K) is partly or wholly determined by its protein component, independent of N-linked and O-linked carbohydrates.