Protein biosynthesis
Protein biosynthesis is the process in which cells build protein. The term is sometimes used to refer only to protein translation, but more often it refers to a multi-step process, beginning with transcription and ending with translation:
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2 Translation 3 Events following biosynthesis 4 External link |
In transcription, the double-stranded DNA is copied into single-stranded mRNA(messenger RNA) by the enzyme RNA polymerase. In eukaryotes, the RNA is likely to be modified after transcription by splicing. Finally, the RNA is inserted into ribosomes. As it is often used, the term protein synthesis typically excludes transcription and describes only the subsequent step of translation (see below).
Protein synthesis consists of a number of stages including: preparing tRNA molecules for use by the ribosome; attaching the ribosome molecule to the mRNA; and the initiation, elongation and termination phases of translation, wherein an amino acid chain forming the basic protein (a polypeptide) is constructed.
During and after its synthesis, a polypeptide chain begins to coil and fold spontaneously and sometimes with the assistance of chaperone proteins to assume secondary and tertiary structure.
Post-translational modification may involve the formation of disulfide bridges and attachment of any of a number of biochemical functional groups, such as acetate, phosphate or various lipids or carbohydrates. Enzymes may also remove one or more amino acids from the leading (amino) end of the polypeptide chain, leacing a protein made up by two polypeptide chains connected by disulfide bonds. In other cases, two or more polypeptides that are synthesized separately may join to become subunits of a protein with quaternary structure.
Transcription
Translation
Events following biosynthesis
External link
