Hua, Z.*

Abstract

In the crowded and confined space of a cell, numerous proteins work collaboratively in various subsystems, such as metabolic pathways, organelle compartments, and complexes, to regulate cell growth and development. Given the estimated concentration ranging from 20% to 30% (w/v) in terms of the total cellular protein [1], the average size of 52 kDa ascribed to human proteins [2,3], and the median 50 μm in diameter of human cells [4], it can be estimated that there are about 1.5 ~ 2.3e+11 protein molecules in one human cell. It has also been estimated that plants, such as Arabidopsis thaliana, have an average protein size and cellular volume similar to those of humans [4,5]. Thus, there are myriad proteins in both human and plant cells. How such a large cohort of proteins is organized and managed for keeping intracellular proteome homeostasis constitutes the central topic in molecular and cellular biology.