User:Minescratcher/sandbox

Protein abundance in cells varies by cell type. The most abundant protein in humans from a whole-organism perspective is TMSB4X by a substantial margin (48363 ppm), followed by APOA2 (21659 ppm), RBP4 (18666 ppm), ALB (15334 ppm), and ORM1 (13790 ppm)). For instance, in human liver cells the most abundant proteins are hemoglobin subunits (20917 ppm of HBA2, 20897 ppm of HBA1, 16993 ppm of HBB) and FABP1, with TMSB4X (11128 ppm) and ALB (9525 ppm) only the 5th and 6th most abundant proteins respectively.

Protein abundance is a significant part of the field of proteomics, especially in disease research. Elevated or reduced levels of specific proteins in cells have been found to be associated with a variety of conditions, including cancer, diabetes, epithelial hyperplasia, sepsis, osteoporosis, epilepsy, various neurodegenerative diseases, and Down syndrome, with potential implications for treatment of some disorders by limiting gene overexpression. Similarly, eyes suffering proliferative vitreoretinopathy have been found to have levels of TGF-β over three times that found in healthy eyes as well as elevated levels of fibronectin, and reduced levels of clusterin were demonstrated in lupus patients. Protein abundance is also a significant tool for evolutionary research. For instance, data from the PaxDB protein abundance database was used to discover reduced levels of sulfur-containing amino acids (cysteine and methionine) in fungi, especially Saccharomycotina, and suggests that more highly expressed proteins tend to be more thermostable.