| Literature References | 1. BARTON, G.J., NEWMAN, R.H., FREEMONT, P.S. AND CRUMPTON, M.J.
Amino acid sequence analysis of the annexin super-gene family of proteins.
EUR.J.BIOCHEM. 198 749-760 (1991).
2. BRAUN, E.L., KANG, S., NELSON, M.A. AND NATVIG, D.O.
Identification of the first fungal annexin: analysis of annexin gene
duplications and implications for eukaryotic evolution.
J.MOL.EVOL. 47 531-543 (1998).
3. BENZ, J. AND HOFMANN, A.
Annexins: from structure to function.
BIOL.CHEM. 378 177-183 (1997).
4. GEISOW, M.J.
Annexins-forms without function but not without fun.
TRENDS BIOTECHNOL. 9 180-181 (1991).
|
| Documentation | The annexins (or lipocortins) are a family of proteins that bind to
phospholipids in a calcium-dependent manner [1]. They are distributed
ubiquitously in different tissues and cell types of higher and lower
eukaryotes, including mammals, fish, birds, Drosophila melanogaster,
Xenopus laevis, Caenorhabtidis elegans, Dictyostelium discoideum and
Neurospora crassa [2,3]. The plant annexins are somewhat distinct from
those found in other taxa [3].
Several distinct annexin subtypes exist, each of which has an amino-acid
sequence consisting of an N-terminal 'arm' followed by 4 or 8 copies of a
conserved domain of 61 residues (only one of these residues, an arginine,
is conserved between all copies). The calcium-binding sites are found in
the repeated domains [4]. Individual repeats (sometimes referred to as
endonexin folds) consist of 5 alpha-helices wound into a right-handed
superhelix. The biological roles of some annexin subtypes is unclear; the
family has been linked with inhibition of phospholipase activity, exo-
cytosis and endoctyosis, signal transduction, organisation of the extra-
cellular matrix, resistance to reactive oxygen species and DNA replication
[2]. Type VI annexin may also play a part in the regulation of some calcium
channels, and its presence may cause arrest of cell growth, before the
DNA-replication stage, in cells growing at low serum concentrations. This
annexin class is unusual in containing 8 repeats of the conserved domain
rather than 4: hence, it is likely that the protein has arisen from a
gene-duplication event.
ANNEXIN VI is a 5-element fingerprint that provides a signature for type VI
annexins. The fingerprint was derived from an initial alignment of 4
sequences: the motifs were drawn from conserved regions spanning the full
alignment length, focusing on those areas that characterise type VI
annexins but distinguish them from other closely related annexin subtypes -
motif 1 lies at the N-terminus; motif 2 resides in the first repeat; motif
3 lies in the second repeat; and motifs 4 and 5 reside between the fourth
and fifth repeats. Two iterations on SPTR41_24f were required to reach
convergence, at which point a true set comprising 7 sequences was identified.
|