Other nucleic acid functions

• Chemical energy sources
• Electron carriers
• Regulatory molecules
• Cofactors

Chemical energy sources: phosphate covalently linked to the 5’ hydroxyl of a ribonucleotide.

Electron carriers: NAD+, the N+ can pick up and drop off two electrons(N+ hydride is unstable with one electron). FAD, has two N to carry electrons and the molecule can pick up one or two electrons (very stable due to resonance). Both FAD and NAD+ have identical lower portion, but their upper portions are not.

Regulatory molecules: signal transducers and secondary messengers such as adenylate cyclase and guanylate cyclase. These molecules stay inside cells and act as cofactors, important for signaling.

Cofactors: Adenosine is present in all of the important ones. Adenosine does not participate in the chemical reaction. Removal of adenosine reduces cofactor function. The cofactors fit into a nucleotide-binding fold. May assist in substrate/active site induced fit.

Nucleotide-binding fold (the Rossman fold): it is a domain that is present in many enzymes and is specific for adenosine nucleotides over others. It is a binding motif or supersecondary structure. Area of a protein that binds nucleotides with specificity (as a motif, they are a pattern found in many proteins). It is composed of alternating beta strands (6) and alpha helices (4).