What is one of the three subunits that all G proteins contain?

G proteins, or guanosine triphosphate-binding proteins, are composed of three distinct subunits known as alpha, beta, and gamma. Among these, the gamma subunit is one of the essential components. The structure of G proteins is important for their function as molecular switches in signal transduction pathways.

The alpha subunit is responsible for binding guanosine diphosphate (GDP) and guanosine triphosphate (GTP) and can dissociate from the beta and gamma subunits when activated. The beta and gamma subunits together form a complex that remains associated after activation and can interact with other cellular proteins. This entire structure allows G proteins to play a crucial role in the transmission of signals from various stimuli to the inside of the cell, affecting numerous physiological processes.

In contrast, the other options provided do not exist as standard subunits of G proteins. Delta and epsilon are not recognized as part of the canonical G protein structure, and omega does not represent a subunit associated with these signaling proteins. Thus, the gamma subunit is correctly identified as one of the three fundamental components of G proteins.