What types of globular proteins are most common in nature?

The most common types of globular proteins in nature are indeed those with two or four subunits. This is primarily because these configurations enable a greater complexity and variety of functions and mechanisms of regulation.

Proteins with two subunits, known as dimers, can effectively interact and regulate each other’s activity, allowing for cooperative binding or allosteric interactions, which are essential for many enzymatic processes and signaling pathways. Examples include hemoglobin, which consists of two alpha and two beta subunits, playing a vital role in oxygen transport.

Proteins with four subunits often form more complex structures, such as tetramers, which can provide enhanced stability and functionality. These proteins can carry out more intricate tasks and are commonly found in enzymes and receptors, where multiple subunits can work together to achieve a dynamic regulation and efficient catalysis.

In comparison, proteins with one, three, five, or six subunits are less common because they do not generally provide the same level of functional versatility or stability as the common dimers and tetramers. Monomeric proteins typically lack the cooperative dynamics that subunit interactions can provide, which can limit their functional capabilities. Therefore, the two and four subunit arrangements are favored in nature for their advantageous properties