pääpolimeraasia

Pääpolimeraasi, known in English as core polymerase, refers to the catalytically active subunit or subunits of an RNA polymerase enzyme. This enzyme is responsible for synthesizing RNA molecules from a DNA template through a process called transcription. In many organisms, particularly bacteria, the RNA polymerase holoenzyme consists of a core enzyme and a sigma factor. The core polymerase alone possesses the enzymatic machinery for RNA synthesis, including the ability to unwind DNA and polymerize ribonucleotides. However, it lacks the ability to initiate transcription at specific promoter sequences. The sigma factor, when bound to the core polymerase, forms the holoenzyme and is crucial for promoter recognition and accurate transcription initiation.

The core polymerase typically comprises multiple subunits, often denoted by Greek letters such as alpha (α), beta (β), beta-prime (β'), and omega (ω). The β and β' subunits are generally considered the catalytic heart of the enzyme, forming the active site where ribonucleotides are added to the growing RNA chain. The α subunits are involved in enzyme assembly and interaction with regulatory proteins. The ω subunit, when present, plays a role in assembly and stability. Prokaryotic core polymerases are essential for basic gene expression, while eukaryotic RNA polymerases have a more complex structure and regulation, with distinct core enzymes for different classes of RNA. Understanding the structure and function of the core polymerase is fundamental to comprehending gene expression and its regulation in all life forms.