Neurokinin A is a member of the tachykinin family of neuropeptide

Neuropeptide

Neuropeptides are small protein-like molecules used by neurons to communicate with each other. They are neuronal signaling molecules, influence the activity of the brain in specific ways and are thus involved in particular brain functions, like analgesia, reward, food intake, learning and...

 neurotransmitters. It is produced from the same preprotachykinin A gene as the neuropeptide

Neuropeptide

Neuropeptides are small protein-like molecules used by neurons to communicate with each other. They are neuronal signaling molecules, influence the activity of the brain in specific ways and are thus involved in particular brain functions, like analgesia, reward, food intake, learning and...

 substance P

Substance P

In the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...

. It has various roles in the body of humans and other animals. One specific example is mediating contraction of the rat

Rat

Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

 colon

Colon (anatomy)

The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...

 and bronchoconstriction through the non-adrenergic non-cholinergic nervous system

Non-noradrenergic, non-cholinergic transmitter

A non-noradrenergic, non-cholinergic transmitter is a neurotransmitter of the peripheral nervous system that is neither of the main two PNS transmitters, i.e. noradrenaline and acetylcholine.-Comparison table:...

 (a branch of the vagal system). Neuropeptide K (which has also been called neurokinin K) and neuropeptide gamma are N-terminally longer versions of neurokinin A, produced from the same splice forms of the same gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

, which appear to be final peptide products in some tissues.

Structure

Structure of mammalian neurokinin A was obtained using CD spectropolarimetry and 2D proton NMR. Analysis showed that in water, the peptide adopts an extended conformation while in the presence of micelle

Micelle

A micelle is an aggregate of surfactant molecules dispersed in a liquid colloid. A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single tail regions in the micelle centre. This phase is...

s (a model cell membrane

Cell membrane

The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...

 system), an alpha helical

Alpha helix

A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...

conformation is induced in the central core (Asp4-Met10).

Further reading