Glutamine synthetase (GS)%3B synthesizes glutamine from glutamate and ammonia%3B with Glt1p%2C forms the secondary pathway for glutamate biosynthesis from ammonia%3B expression regulated by nitrogen source and by amino acid limitation%3B forms filaments of back-to-back stacks of cylindrical homo-decamers at low pH%2C leading to enzymatic inactivation and storage during states of advanced cellular starvation%3B relocalizes from nucleus to cytoplasmic foci upon DNA replication stress