InterPro: IPR000243 Peptidase T1A, proteasome beta-subunit

In the MEROPS database peptidases and peptidase homologues are grouped into clans and families. Clans are groups of families for which there is evidence of common ancestry based on a common structural fold:

• Each clan is identified with two letters, the first representing the catalytic type of the families included in the clan (with the letter 'P' being used for a clan containing families of more than one of the catalytic types serine, threonine and cysteine). Some families cannot yet be assigned to clans, and when a formal assignment is required, such a family is described as belonging to clan A-, C-, M-, S-, T- or U-, according to the catalytic type. Some clans are divided into subclans because there is evidence of a very ancient divergence within the clan, for example MA(E), the gluzincins, and MA(M), the metzincins.
• Peptidase families are grouped by their catalytic type, the first character representing the catalytic type: A, aspartic; C, cysteine; G, glutamic acid; M, metallo; S, serine; T, threonine; and U, unknown. The serine, threonine and cysteine peptidases utilise the amino acid as a nucleophile and form an acyl intermediate - these peptidases can also readily act as transferases. In the case of aspartic, glutamic and metallopeptidases, the nucleophile is an activated water molecule.

In many instances the structural protein fold that characterises the clan or family may have lost its catalytic activity, yet retain its function in protein recognition and binding.

Threonine peptidases are characterised by a threonine nucleophile at the N terminus of the mature enzyme. The threonine peptidases belong to clan PB or are unassigned, clan T-. The type example for this clan is the archaean proteasome beta component of Thermoplasma acidophilum.

Proteins in this entry are threonine peptidases belonging to MEROPS peptidase family T1 (clan PB(T)), subfamily T1A.

The proteasome (or macropain) (EC:3.4.25.1) [1, 2, 3, 4, 5] is a eukaryotic and archaeal multicatalytic proteinase complex that seems to be involved in an ATP/ubiquitin-dependent nonlysosomal proteolytic pathway. In eukaryotes the proteasome is composed of about 28 distinct subunits which form a highly ordered ring-shaped structure (20S ring) of about 700 kDa. Most proteasome subunits can be classified, on the basis on sequence similarities into two groups, alpha (A) and beta (B). The beta subunit sequences are T1A peptidases which range from 190 to 290 amino acids in length.