proteinSH

proteinSH is a fictional or placeholder protein commonly used in teaching materials and computational benchmarks to illustrate core concepts in protein science. It does not correspond to a specific naturally occurring protein or organism.

Typically described as a single-domain globular protein of roughly 20–28 kDa, proteinSH is predicted to adopt an all-alpha/beta mixed fold with a solvent-exposed active site neighborhood housing a catalytic cysteine-histidine dyad.

In educational models, proteinSH functions as a thiol-disulfide oxidoreductase that catalyzes thiol-disulfide exchange in model substrates. The proposed mechanism involves nucleophilic attack by the catalytic cysteine on a substrate disulfide to form a mixed disulfide intermediate, followed by resolution to release the reduced substrate and regenerate the active site.

In simulations and classroom experiments, proteinSH is often expressed in Escherichia coli or produced synthetically; mutations in the cysteine or histidine residues alter activity consistent with a dyad mechanism.

As a benchmark, proteinSH provides a closed system for testing protein structure prediction, docking, docking scoring, and enzyme design algorithms. It also helps illustrate the relationship between sequence, fold, and function.

The term proteinSH appears in pedagogical resources and is treated as a hypothetical reference standard rather than a characterized natural protein.