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Modular organization of inteins and C‐terminal autocatalytic domains
Author(s) -
Pietrokovski Shmuel
Publication year - 1998
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560070106
Subject(s) - intein , homing endonuclease , protein splicing , rna splicing , endonuclease , biology , protein engineering , genetics , cleavage (geology) , protein domain , protein tag , computational biology , dna , biochemistry , enzyme , gene , fusion protein , rna , paleontology , fracture (geology) , recombinant dna
Analysis of the conserved sequence features of inteins (protein “introns”) reveals that they are composed of three distinct modular domains. The N‐terminal (N) and C‐terminal (C) domains are predicted to perform different parts of the autocatalytic protein splicing reaction. An optional endonuclease domain (EN) is shown to correspond to different types of homing endonucleases in different inteins. The N domain contains motifs predicted to catalyze the first steps of protein splicing, leading to the cleavage of the intein N terminus from its protein host. Intein N domain motifs are also found in C‐terminal autocatalytic domains (CADs) present in hedgehog and other protein families. Specific residues in the N domain of intein and CADs are proposed to form a charge relay system involved in cleaving their N‐termini. The intein C domain is apparently unique to inteins and contains motifs that catalyze the final protein splicing steps: ligation of the intein flanks and cleavage of its C terminus to release the free intein and spliced host protein. All intein EN domains known thus far have dodecapeptide (DOD, LAGLI‐DADG) type homing endonuclease motifs. This work identifies an EN domain with an HNH homing‐endonuclease motif and two new small inteins with no EN domains. One of these small inteins might be inactive or a “pseudo intein.” The results suggest a modular architecture for inteins, clarify their origin and relationship to other protein families, and extend recent experimental findings on the functional roles of intein N, C, and EN motifs.