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A protein precursor, also called a pro-protein or pro-peptide, is an inactive protein (or peptide) that can be turned into an active form by post-translational modification, such as breaking off a piece of the molecule or adding on another molecule. The name of the precursor for a protein is often prefixed by pro-.
In chemistry, a precursor is a compound that participates in a chemical reaction that produces another compound. In biochemistry , the term "precursor" often refers more specifically to a chemical compound preceding another in a metabolic pathway , such as a protein precursor .
For example, a precursor mRNA (pre-mRNA) is a type of primary transcript that becomes a messenger RNA (mRNA) after processing. Pre-mRNA is synthesized from a DNA template in the cell nucleus by transcription. Pre-mRNA comprises the bulk of heterogeneous nuclear RNA (hnRNA).
The pre-mRNA processing at the 3' end of the RNA molecule involves cleavage of its 3' end and then the addition of about 250 adenine residues to form a poly(A) tail.The cleavage and adenylation reactions occur primarily if a polyadenylation signal sequence (5'- AAUAAA-3') is located near the 3' end of the pre-mRNA molecule, which is followed by another sequence, which is usually (5'-CA-3') and ...
In cell biology, precursor cells—also called blast cells—are partially differentiated, or intermediate, and are sometimes referred to as progenitor cells. A precursor cell is a stem cell with the capacity to differentiate into only one cell type, meaning they are unipotent stem cells .
Precursors in the Halo series, an extremely advanced race that preceded and were destroyed by The Forerunners; Precursor, a 1999 novel set in C. J. Cherryh's Foreigner universe; Precursors, a fictional race (now extinct) of ancient beings in the board game Cosmic Encounter; Precursors, a fictional alien race in the Star Control video game series
Animal miRNAs are initially transcribed as part of one arm of an ~80 nucleotide RNA stem-loop that in turn forms part of a several hundred nucleotide-long miRNA precursor termed a pri-miRNA. [ 56 ] [ 52 ] When a stem-loop precursor is found in the 3' UTR, a transcript may serve as a pri-miRNA and a mRNA. [ 52 ]
In polymer chemistry, the term prepolymer or pre-polymer, refers to a monomer or system of monomers that have been reacted to an intermediate-molecular mass state. This material is capable of further polymerization by reactive groups to a fully cured, high-molecular-mass state.