The Wheat Breadmaking (TaWBM) gene, initially discovered through a screening for factors affecting flour quality, has been linked to the rising of bread dough due to its expression in seed endosperm. Notably, homologs of the Wbm gene are found not only in wheat but also in other cereal species, including oats, rye, and barley. Despite this, the WBM protein has yet to be experimentally characterized. In this study, we identified a group of WBM-like Seed Proteins (WSPNs) within the prolamin fraction of barley flour. We used several different genetic techniques to study the function of WSPN genes. A genomic analysis showed that WSPNs are encoded by three tightly clustered genes, located on chromosome 7H's long arm. The genes are expressed exclusively during the development of grain endosperm. The WSPNs share a consistent gene structure, featuring a single exon with open reading frames ranging from 253 to 313 base pairs. The first 80 base pairs code for a sorting peptide. Additionally, these genes contain a conserved motif (C–P-X-G-X4-C-X(4–8)-C-X-C), and our structural predictions suggested that this motif forms a microdomain of two antiparallel strands, with aligned cysteine residues. The presence of post-translationally modified proteins was confirmed by means of mass spectrometry.