TES (protein)

'TES' (aka 'Testin') is the protein product of the TESS gene, located on chromosome 7 in Homo sapiens. TES is a 47 kDa protein composed of 421 amino acids found at focal adhesions and is thought to have a role in regulation of cell motility. In addition to this, TES functions as a tumour suppressor ; the TESS gene is located within a fragile region of chromosome 7, and the promoter elements of the TESS gene have been shown to be susceptible to methylation - this prevents the expression of the TES protein.

Domain Organisation
Tes is composed of the following domains:

The structures of the Cysteine rich domain and the PET domain are not known. LIM domains, however, are known as modulators of protein interactions . LIM domain consist of 2 zinc fingers separated by 2 hydrophobic amino acids (generally a Phenylalanine and then a Leucine.

Binding Partners
TES does not appear to be an enzyme; rather it is a protein that mediates/regulates cullular functions via Protein:protein interactions. Pull down experiments reveal that TES has putative interactions mediated by the indicated domain:

Garalov et al showed that the interaction between TES & zyxin were direct, using recombinant proteins expressed in E.coli.

Some of the potential binding partners (Zyxin, mENA) can be found in focal adhesion complexes; the range of binding partners indicates a potential role for TES in-between 'privileged' Actin polymerisation and focal adhesion contacts to the extracellular matrix. This tallies with the observation that GFP-tagged TES can be seen at focal adhesions.

Conformational Change
Based on the observations that: Garalov et al propose that TES exists in two conformational states: A 'closed' state where the N & C halves of TES interact, obscuring the Zyxin binding site in LIM1, and an 'open' state where the Zyxin binding site is accessible and the two halves no-longer interact in the same fashion, if at all. The regulatory mechanism switching between the two states is not presently fully understood.
 * Mammalian cell derived TES binding Zyxin
 * E.coli produced recombinant TES (rTES) does not bind Zyxin
 * An rTES construct composed of residues 201-421 (i.e, the linker and all 3 LIM domains) does bind Zyxin
 * The above rTES construct binds an N-terminal rTES construct, consisting of the cysteine rich and PET domains - IE, the two halves of TES interact with each other.

Phenotype
In RNAi experiments, cells that had impaired TES expression showed an inability to correctly organise their focal adhesions and actin stress fibres.

In gene knockout experiments, transgenic mice lacking both copies of the TES gene displayed an increased susceptibility to tumour formation when challenged with a carcinogen. Mice retaining the TES gene were less susceptible: thus, TES is a tumour suppressor gene.