| Literature References | 1. MICHALAK, M., MILNER, R.E., BURNS, K. AND OPAS, M.
Calreticulin
BIOCHEM.J. 285 681-692 (1992).
2. BERGERON, J.J.M., BRENNER, M.B., THOMAS, D.Y. AND WILLIAMS, D.B.
Calnexin - a membrane-bound chaperone of the endoplasmic-reticulum.
TRENDS BIOCHEM.SCI. 19 124-128(1994).
3. WATANABE, D., YAMADA, K., NISHINA, Y., TAJIMA, Y., KOSHIMIZU, U.,
NAGATA, A. AND NISHIMUNE, Y.
Molecular-cloning of a novel ca2+-binding protein (calmegin) specifically
expressed during male meiotic germ-cell development.
J.BIOL.CHEM. 269 7744-7749 (1994).
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| Documentation | Calreticulin is a high-capacity calcium-binding protein found in most
tissues [1]. It is located at the periphery of the endoplasmic and
sarcoplamic reticulum membranes, where it is thought to play a role in
lumenal calcium storage. The protein contains ~400 amino acid residues,
distributed between 3 domains: an N-terminal, possibly globular, 180-
residue `N-domain'; a central ~70-residue `P-domain', containing 3 repeats
of a 17-residue acidic motif that binds calcium with a low-capacity but
high-affinity; and a C-terminal `C-domain' (rich in both acidic residues
and lysine) that binds calcium with a high-capacity but low-affinity.
Calreticulin is evolutionarily related to several other calcium-binding
proteins, including Onchocerca volvulus antigen RAL-1, calnexin [2] and
calmegin [3].
CALRETICULIN is a 6-element fingerprint that provides a signature for the
calreticulins. The fingerprint was derived from an initial alignment of
8 sequences: the motifs were drawn from short conserved regions spanning
virtually the full alignment length - motifs 1 and 2 lie in the N-domain
and include the regions encoded by PROSITE patterns CALRETICULIN_1 (PS00803)
and CALRETICULIN_2 (PS00804); motifs 3 and 4 lie in the P-domain, and
include the repeat region encoded by PROSITE pattern CALRETICULIN_3
(PS00805); and motif 5 lies at the end of this region, just prior to the
C-domain. Two iterations on OWL29.0 were required to reach convergence,
at which point a true set comprising 43 sequences was identified. Several
partial matches were also found, all of which are fragments.
An update on SPTR37_9f identified a true set of 43 sequences.
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