PROSITE documentation PDOC52033
Latexin (LXN)-type cystatin domain profile


Latexin (LXN), or tissue carboxypeptidase inhibitor (TCI), is the only known mammalian carboxypeptidase inhibitor (CPI). LTX has no detectable sequence similarity with plant and parasite inhibitors, but it is related to a human putative tumor suppressor protein, TIG1. TIG1 is larger than latexin, and the additional residues are thought to encode a membrane anchor at the N terminus. Other proteins with sequence identity to latexin are found in chicken (ovocalyxin-32) and Xenopus, but no related proteins were found in nonvertebrates. Chicken ovocalyxin-32 is a protein involved in egg shell production [1,2].

The structure of LXN shows no structural relationship with other CPIs. Furthermore, despite a lack of detectable sequence duplication, the structure incorporates two topologically analogous domains related by pseudo two-fold symmetry. Each domain comprises a curved five-stranded antiparallel β sheet wrapped around an α helix (see <PDB:1WNH>). These domains share a cystatin fold architecture found in proteins that inhibit cysteine proteases, suggesting an evolutionary and possibly functional relationship. LXN may have evolved from an ancestral cystatin-like protein as a consequence of a gene duplication event. The LXN-type cystatin domains are packed against each other through the helices and linked by a connecting segment encompassing a third α-helix. The two domains are arranged so that there is a cleft in this part of the structure that can accommodate a peptide chain [1,2].

The profile we developed covers the LXN-type cystatin domain.

Last update:

July 2023 / First entry.


Technical section

PROSITE method (with tools and information) covered by this documentation:

CYSTATIN_LXN, PS52033; Latexin (LXN)-type cystatin domain profile  (MATRIX)


1AuthorsAagaard A. Listwan P. Cowieson N. Huber T. Ravasi T. Wells C.A. Flanagan J.U. Kellie S. Hume D.A. Kobe B. Martin J.L.
TitleAn inflammatory role for the mammalian carboxypeptidase inhibitor latexin: relationship to cystatins and the tumor suppressor TIG1.
SourceStructure 13:309-317(2005).
PubMed ID15698574

2AuthorsPallares I. Bonet R. Garcia-Castellanos R. Ventura S. Aviles F.X. Vendrell J. Gomis-Rueth F.X.
TitleStructure of human carboxypeptidase A4 with its endogenous protein inhibitor, latexin.
SourceProc. Natl. Acad. Sci. U. S. A. 102:3978-3983(2005).
PubMed ID15738388

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