Hypusine is an uncommon
amino acid
Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
found in all
eukaryote
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
s and in some
archaea
Archaea ( ) is a Domain (biology), domain of organisms. Traditionally, Archaea only included its Prokaryote, prokaryotic members, but this has since been found to be paraphyletic, as eukaryotes are known to have evolved from archaea. Even thou ...
, but not in
bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
. The only known proteins containing the hypusine residue is
eukaryotic translation initiation factor 5A (eIF-5A) and a similar protein found in archaea. In humans, two isoforms of eIF-5A have been described: eIF5A-1 and eIF5A-2. They are encoded by two distinct genes
EIF5A and
EIF5A2. The protein is involved in
protein biosynthesis
Protein biosynthesis, or protein synthesis, is a core biological process, occurring inside Cell (biology), cells, homeostasis, balancing the loss of cellular proteins (via Proteolysis, degradation or Protein targeting, export) through the produc ...
and promotes the formation of the first
peptide bond. The region surrounding the hypusine residue is
highly conserved and is essential to the function of eIF5A. Thus, hypusine and eIF-5A appear to be vital for the viability and proliferation of eukaryotic cells.
Hypusine is formed in eIF-5A by
post-translational modification of one of the
lysyl residues. Two reactions and two enzymes are involved:
*1.
Deoxyhypusine synthase catalyzes the cleavage of the polyamine
spermidine and transfer of its 4-aminobutyl moiety to the ε-amino group of one specific lysine residue of the eIF-5A precursor to form deoxyhypusine and
1,3-diaminopropane.
*2.
Deoxyhypusine hydroxylase mediates the formation of hypusine by addition of a hydroxyl group to the deoxyhypusine residue.
An excess of hypusine was found in the urine of children and patients with familial
hyperlysinemia.
Hypusine was first isolated from bovine brain by Japanese scientists Shiba ''et al.'' in 1971.
The name ''hypusine'' indicates that the molecule comprises moieties of hydroxyputrescine and lysine.
See also
*
''n''-Butylamine, related to 4-aminobutyl group of deoxyhypusine
*
Putrescine
Putrescine is an organic compound with the formula (CH2)4(NH2)2. It is a colorless solid that melts near room temperature. It is classified as a diamine. Together with cadaverine, it is largely responsible for the foul odor of Putrefaction, putref ...
*
Polyamine
*
EIF5A
*
EIF5A2
*
Diphthamide, another translation-related uncommon amino acid
**
EEF2, eukaryotic elongation factor 2, utilizing diphthamide
References
Alpha-Amino acids
Non-proteinogenic amino acids
{{Non-proteinogenic amino acids