proteomics
Meaning of proteomics: The large-scale study of every protein a cell is making, a picture that changes far faster than its genes do.
Definition of proteomics
Proteomics is the large-scale study of all the proteins present in a cell, tissue or organism at one moment. It measures which proteins are there, how much of each, how they have been chemically modified, and which ones bind to one another. Unlike the genome, this set shifts constantly with the conditions the cell meets.
Why study proteins rather than genes?
The genome is a fixed list of instructions and is nearly identical in every cell of the body. It does not reveal which instructions are being followed. Proteins are the machines that do the work, and their number, position and activity differ between a liver cell and a nerve cell using the same genome. Counting the messenger molecules that carry instructions from gene to protein helps, but only partly, because a message can sit unread and a finished protein can be switched on or off afterward by chemical tags. Proteomics measures the working parts directly.
How is it done?
Proteins from a sample are first chopped into short fragments by an enzyme. Those fragments are separated by liquid chromatography and fed into a mass spectrometer, an instrument that weighs molecules with great precision. Each fragment is weighed, broken apart, and its pieces weighed again. The resulting pattern is matched against a database predicting what every fragment of every known protein should weigh. Thousands of proteins can be identified from a single sample in this way, and the strength of each signal indicates how much is present.
What does it show that a gene list cannot?
| Question | What proteomics adds |
|---|---|
| Is the protein present | Detects the protein itself, not the instruction for it |
| Has it been modified | Finds added tags that switch activity on or off |
| What does it bind | Identifies partner proteins pulled down alongside it |
| Where is it | Places proteins in particular compartments of the cell |
What is it used for?
The commonest use is comparison: proteins from diseased tissue set against proteins from healthy tissue, or samples taken before and after treatment. Differences point to candidate markers and to the pathways involved. The approach has been applied to tumor classification, to the study of immune function, and to identifying bacteria in the laboratory, where a mass spectrum now names an organism within minutes. It complements gene-based methods such as fluorescence in situ hybridization rather than replacing them. The chief limitation is range: a handful of abundant proteins dominate blood, and the interesting ones often lie in vanishingly small amounts beneath them.
Used in a sentence
Proteomics was used to compare protein expression between tumor tissue and adjacent normal tissue.
Good to know
The set of proteins in a cell shifts with conditions, so a proteomic result describes one moment rather than a fixed property in the way a gene sequence does.
Word origin
Where “proteomics” comes from
Protein comes from the Greek proteios, meaning of first rank; the ending -omics follows genomics and marks the study of a complete set.