Protein domains/Overview

Every protein coding sequence in the Registry consists of at least three protein domains, a head domain, one or more internal domains, and a tail domain.

1. Head: The Head domain consists of the start codon followed immediately by zero or more triplets specifiying an N-terminal tag, such as a protein export tag or lipoprotein binding tag.
2. Domains: Protein domains consist of a series of codon triplets coding for an amino acid sequence without a start codon or stop codon. Multiple Domains can be fused.
3. Special Domains: Short Domains with specific function may be separately categorized, but obey the same composition rules as normal domains. Special domains include tags, linkers, cleavage sites, and intein sites.
4. Tail: The C-terminus of a coding region consists of zero or more triplet codons, followed by a pair of TAA stop codons. In the simplest case, the stop codons terrminate the protein with an Stop. More complex Tails may include degradation tags appropriate to the organism (i.e., with different degradation rates).

Thus protein coding sequences can, in some sense, be thought of as a composite of three or more protein domains. Most protein coding sequences available from the Registry consist of a particularly simple Head domain (the start codon), a single internal domain, and a simple Tail domain (the stop codon). However, we envision that more and more iGEM teams and labs will design Head, Internal, Special and Tail protein domains and assemble them in different combinations.