Regulation of glutamine synthetase from the white button mushroom Agaricusbisporus

The regulation of glutamine synthetase (GS) from Agaricus bisporus was stud ied at the posttranscriptional level using a specific antibody fraction dir ected against purified GS. The cross-reactivity of the antiserum against va rious Agaricus species and other fungi was tested and low reactivity with t he Ascomycetes was found. GS protein and activity levels were measured in c ell-free extracts of mycelium grown on different N sources. In mycelium gro wn on glutamine or ammonium as N source, the biosynthetic GS activity is hi gher than the transferase activity. Moreover, the results show a correlatio n between GS biosynthetic activity, GS protein, and previously reported mRN A levels. Also, after addition of ammonium or glutamine to glutamate-utiliz ing cultures, transferase activity decreased more rapidly than biosynthetic activity and GS protein level. This suggests a conformational modification which only affects transferase activity. (C) 1999 Academic Press.