Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.3.1.108 (TAT)
 2,389 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Yeast mutants modifying the C-terminal region of mitochondrial cytochrome b were isolated and characterized. A nonsense mutation of the leucine codon 335 (TTA-->TAA), 50 residues before the normal C-terminus, blocks incorporation of heme into the apocytochrome b and prevents growth on non-fermentable substrates. The same defects were observed in a frameshift mutant (after codon 348, TAT-->TATT) in which the last 37 C-terminal residues are predicted to be replaced by a novel sequence of 33 amino acids. Function was regained in the nonsense mutant only by true back mutations restoring a protein of the wild-type sequence. The respiratory capacity was restored to wild-type levels in the frameshift mutant by a variety of single base subtractions located within a window of 24 bases before or after the original +T addition, these pseudo-reversions resulted in single or multiple (up to five) consecutive amino acid replacements between positions 346 and 354 and restored the wild-type sequence from position 355 to 385. These data, combined with hydropathy calculations and sequence comparisons, suggest that the C-terminal domain of cytochrome b forms a transmembrane segment essential for the correct assembly of the cytochrome bc1 complex.
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PMID:The C-terminal domain of yeast cytochrome b is essential for a correct assembly of the mitochondrial cytochrome bc1 complex. 839 6

The Rieske Fe/S protein, a nuclear-encoded subunit of the cytochrome b(6)/f complex in chloroplasts, is retarded in the stromal space after import into the chloroplast and only slowly translocated further into the thylakoid membrane system. As shown by the sensitivity to nigericin and to specific competitor proteins, thylakoid transport takes place by the DeltapH-dependent TAT pathway. The Rieske protein is an untypical TAT substrate, however. It is only the second integral membrane protein shown to utilize this pathway, and it is the first authentic substrate without a cleavable signal peptide. Transport is instead mediated by the NH(2)-terminal membrane anchor, which lacks, however, the twin-arginine motif indicative of DeltapH/TAT-dependent transport signals. Furthermore, transport is affected by sodium azide as well as by competitor proteins for the Sec pathway in chloroplasts, demonstrating for the first time some cross-talk of the two pathways. This might take place in the stroma where the Rieske protein accumulates after import in several complexes of high molecular mass, among which the cpn60 complex is the most prominent. These untypical features suggest that the Rieske protein represents an intermediate or early state in the evolution of the thylakoidal protein transport pathways.
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PMID:The Rieske Fe/S protein of the cytochrome b6/f complex in chloroplasts: missing link in the evolution of protein transport pathways in chloroplasts? 1152 15