Final answer:
GCN4 is identified as a transcription factor that is part of the GNAT superfamily, playing a key role in the GAAC mechanism in yeast and regulating the transcription of genes responsible for amino acid synthesis and various cellular processes.
Step-by-step explanation:
The two domain structure of GCN4 and its activity identify it as a transcription factor. Specifically, GCN4 is part of the GNAT superfamily of proteins, involved in a broad range of functions such as histone acetylation and amino acid biosynthesis. GCN4 plays a critical role in the General Amino Acid Control (GAAC) mechanism in yeast and is essential in responding to amino acid starvation by up-regulating the transcription of genes involved in amino acid synthesis. It is also involved in the regulation of various other cellular stress responses and metabolic processes, affecting up to 10% of all yeast genes. The GNAT superfamily proteins are notable for their ability to bind with CoA-SH and, through evolutionary diversification, they present various functions including acetylation of specific substrates.
Furthermore, the GNAT superfamily includes enzymes like histone acetyltransferases and aminoglycoside N-acetyltransferases, which use acyl-S-CoA to acylate their substrates. The structure of these proteins typically contains a core region formed by ß-strands and helices, which is conserved across the family, emphasizing their functional importance in cellular mechanisms such as translational regulation. The study of GCN4 and related GNAT superfamily members provides insights into the complex regulation of gene expression in response to cellular needs and environmental cues.