Good quality durum wheats usually present the LMW-2 type of SDS-PAGE pattern, whereas the LMW-1 type of pattern is usually associated with poor quality durum wheats. The two patterns are distinguished mainly by the presence of a strongly expressed protein band with molecular weight around 42,000 (42 K subunit) in the LMW-2-type pattern; this subunit is absent in the LMW-1-type pattern. Here we show that this particular low-molecular-weight glutenin subunit has strong similarity to a subunit present in some bread wheat cultivars. This correspondence has been demonstrated through SDS-PAGE, PCR analysis of the corresponding genes, a comparison of the deduced amino acid sequences, and RP-HPLC. This last approach showed a slight difference in retention time between the 42 K protein of bread and durum wheats that might be attributed to the eight amino acid differences found between the deduced amino acid sequences of the two corresponding genes.