Protein expression refers to the way proteins are modified, synthesized, and regulated in living organisms. In protein testing, the term can be applied either to the subject of an investigation or to the laboratory techniques required for protein production. 

This article focuses on the importance of protein expression. In practice, however, the production of recombinant proteins relies on the use of cellular machinery. If you are looking for information on recombinant protein expression visit

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Introduction to Protein Expression

Proteins are synthesized and regulated according to the functional requirements of the cell. The protein scheme is stored in DNA and translated by a highly regulated transcription process to produce messenger RNA. The message encoded by the mRNA is then converted into a protein. 

Transcription is the transfer of information from DNA to MRNA, and translation is the synthesis of proteins based on the sequence determined by the MRNA.

Simple transcription and translation scheme. It describes the entire flow of information from base pairs of DNA sequences (genes) to polypeptide sequences of amino acids (proteins).

In prokaryotes, translation and transcription occur simultaneously. MRNA translation begins before the mature MRNA transcript is fully synthesized. This simultaneous transcription and translation of genes is called transcription and related translation. 

In eukaryotes, processes are spatially separated and proceed sequentially, with transcription occurring in the cell nucleus and translation or protein synthesis in the cytoplasm.