The most abundant protein on earth surface is:

Explanation:

Rubisco (d-ribulose 1,5-bisphosphate carboxylase/oxygenase) is responsible for the vast majority of global carbon fixation and has been claimed to be the most abundant protein on Earth.

The most abundant protein in nature is probably the chloroplast enzyme ribulose bisphosphate carboxylase/oxygenase (Fraction I protein).

• It is arguably the most important enzyme because it catalyses the carbon dioxide-fixing step in photosynthesis.
• The synthesis of this protein depends upon the interaction of nucleargenes with the genetic system located in the chloroplast, and involves the transfer of polypeptides across the chloroplast envelope by a post-translational mechanism.