title: Staphylococcal enterotoxin A gene is associated with a variable genetic element.
abstract: The genetic determinant of Staphylococcus aureus enterotoxin A (SEA) has been cloned in pBR322 in Escherichia coli and found to be expressed and secreted into the periplasmic space in that organism. The SEA gene (entA) is within a 2.5-kilobase-pair HindIII fragment that is part of a discrete genetic element 8-12 kilobase pairs in length. This entA element has a standard chromosomal location [between the purine (pur) and isoleucine-valine (ilv) markers] in most S. aureus strains. In some strains it is unlinked to pur-ilv. However, its internal structure is conserved at different locations. Some naturally occurring SEA-nonproducer (EntA-) strains lack the entire entA element, and one instance of its spontaneous loss is reported. Other naturally occurring strains have EntA- structural variants of the element at the same pur-ilv location at which the intact element is most commonly found. Some of these strains are EntA-, others are EntA+; the latter have a second, unlinked copy of the element containing their functional entA gene. These results suggest that entA is associated with a structurally unstable, possibly mobile, discrete genetic element.
mesh_terms: D004262:DNA Restriction Enzymes; D004768:Enterotoxins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D005796:Genes; D005798:Genes, Bacterial; D005838:Genotype; D009693:Nucleic Acid Hybridization; D010957:Plasmids; D013045:Species Specificity; D013211:Staphylococcus aureus / Q000235:genetics*
chemical_list: D004768:Enterotoxins; C026066:enterotoxin A, Staphylococcal; D004262:DNA Restriction Enzymes