Description
Protoplast secreted protein 1 (Pst1) is an anchored plasma membrane protein. Pst1 was previously identified as a protein secreted by yeast regenerating protoplasts, which suggests a role in cell wall construction (1). Pst1 is a protein with 444 amino acids and is attached to yeast cell wall via a glycosylphosphatidylinisotol (GPI) anchor (2). Pst1 contains 15 potential N-linked glycosylation sites and is heavily glycosylated. It migrates at around 200 kDa on SDS-PAGE when produced in wild type S. cerevisiae. Our Pst1 protein was expressed in a genetically manipulated triple-mutant (TM) S. cerevisiae stain (deltaoch1 deltamnn1 deltamnn4), which results in the production of sole Man8GlcNAc2 carbohydrate structures and Pst1 migration at approximately 100 kDa. When produced in the TM yeast, Pst1 can be recognized by several HIV-1 broadly neutralizing antibodies, including 2G12 and recently identified glycan-specific PGT antibodies (3). Among several heavily N-glycosylated TM yeast glycoproteins, Pst1 shows high affinity for 2G12 and efficiently inhibits gp120 interactions with 2G12 and DC-SIGN, and it also blocks 2G12-mediated neutralization of HIV-1 pseudoviruses (4)