Disease relevance of Inteins

• The DnaE split intein from Synechocystis sp. PCC6803 was used to cyclize the Escherichia coli enzyme dihydrofolate reductase and to produce the cyclic, eight-amino acid tyrosinase inhibitor pseudostellarin F in bacteria [1].
• Mycobacterium tuberculosis recA harbors an intervening sequence in its open reading frame, presumed to encode an endonuclease (PI-MtuI) required for intein homing in inteinless recA allele [2].
• We have determined the crystal structure of a 154-residue intein derived from the dnaB gene of Synechocystis sp. strain PCC6803 and refined it to a 2.0-A resolution [3].
• Naturally split inteins are only known in the DNA polymerase III alpha subunit (polC or dnaE gene) of a few cyanobacteria [4].
• Two cytotoxic proteins, bovine pancreatic ribonuclease A (RNase A), and a restriction endonuclease from Haemophilus parainfluenzae (HpaI), were produced using a novel semisynthetic approach that utilizes a protein splicing element, an intein, to generate a reactive thioester at the C-terminus of a recombinant protein [5].

High impact information on Inteins

• This review focuses on the mechanisms underlying biogenesis of the mature Hh proteins, which are dually modified by cholesteryl and palmitoyl adducts, as well as on the relationship between Hh proteins and the self-splicing proteins (i.e., proteins containing inteins) and the Hh-like proteins of nematodes [6].
• The conserved Ser or Cys at the intein N-terminus and the conserved intein penultimate His are absent in the KlbA family of inteins [7].
• Protein splicing of the yeast TFP1 intervening protein sequence: a model for self-excision [8].
• We have synthesized artificial genes that encode for N-terminal half (Int-n) and C-terminal half (Int-c) fragments of Ssp DnaE split intein and divided beta-glucuronidase (GUS) gene to encode GUS-n and GUS-c parts of the enzyme as reporter [9].
• Although apparently unrelated evolutionarily, Nup98 has converged on an autoproteolytic biogenesis mechanism similar to that of hedgehog proteins, the inteins, and the N-terminal nucleophile proteins [10].

Chemical compound and disease context of Inteins

• The smallest known intein, found in the ribonucleoside diphosphate reductase gene of Methanobacterium thermoautotrophicum (Mth RIR1 intein), was found to splice poorly in Escherichia coli with the naturally occurring proline residue adjacent to the N-terminal cysteine of the intein [11].
• The first naturally occurring split intein was found in the dnaE gene of Synechocystis sp. PCC6803 and belongs to a subclass of inteins without a penultimate histidine residue [12].
• Mycobacterium tuberculosis RecA intein, a LAGLIDADG homing endonuclease, displays Mn(2+) and DNA-dependent ATPase activity [13].

Biological context of Inteins

• The downstream bnrdE exon harbors an intervening sequence not excised at the level of the primary transcript, which encodes an in-frame polypeptide displaying all the features of an intein [14].
• Cyclization of this residue to succinimide causes the final detachment of inteins from their hosts [15].
• Both recombinant inteins exhibit endonuclease activity, with an optimal temperature of 70 degrees C. The Tfu pol-1 intein, which belongs to the Psp KOD pol-1 allelic family, recognizes and cleaves a minimal sequence of 16 base pairs (bp) on supercoiled DNA with either Mn(2+) or Mg(2+) as cofactor [16].
• Three inteins were found when analyzing a pair of split dnaE genes encoding the catalytic subunit of DNA polymerase III in the oceanic N2-fixing cyanobacterium Trichodesmium erythraeum [17].
• The FKBP and FRB domains, which are dimerized by rapamycin and thereby induce the reconstitution of the split intein, were fused to the extein sequences of the split intein halves [18].

Anatomical context of Inteins

• The host gene of the Cryptococcus intein, PRP8, encodes a highly conserved mRNA splicing protein found as part of the spliceosome [19].

Associations of Inteins with chemical compounds

• Using site-directed mutagenesis, the N-terminal cysteine, proposed as the nucleophile in the first step of the splicing reaction, was changed to a Ser 1 and Ala 0, thus capturing the intein in a pre-spliced state [20].
• The conserved and essential residues of precursor proteins consist of an asparagine as the last residue of the intein and a hydroxyl- or thiol-containing residue immediately following both splice junctions [21].
• Protein splicing in the absence of an intein penultimate histidine [22].
• Protein splicing of inteins with atypical glutamine and aspartate C-terminal residues [15].
• Zinc ion also inhibited hydroxylamine-dependent N-terminal cleavage of the RecA intein [23].

Gene context of Inteins

• In addition, bnrdE provides an example of a group I intron and an intein coding sequence within the same gene [14].
• We show that a 113 residue truncated Ho-endonuclease starting at intein motif C initiates a mating type switch in yeast [24].
• CONCLUSION: The repairing system working in intein homing shares molecular machinery with meiotic recombination induced by Spo11p [25].
• The Cne PRP8 intein may be a useful drug target in addressing the cryptococcal infections so prevalent in AIDS patients [19].
• We describe the phylogenetic relationships among the four eukaryote nuclear encoded inteins (VMA, PRP8, GLT1 and CHS2) [26].

Analytical, diagnostic and therapeutic context of Inteins

• Rational protein engineering was then combined with genetic selection to evolve an additional intein whose activity is controlled by the presence of synthetic estrogen ligands [27].
• The mutant forms of PAI-1 containing the chitin-binding intein tag were then purified using affinity chromatography wherein the intein tag is cleaved, leaving mutant PAI-1 protein [28].

References