scsB, a cDNA encoding the hydrogenosomal beta subunit of succinyl-CoA synthetase from the anaerobic fungus Neocallimastix frontalis.
A clone containing a Neocallimastix frontalis cDNA assumed to encode the beta subunit of succinyl-CoA synthetase (SCSB) was identified by sequence homology with prokaryotic and eukaryotic counter-parts. An open reading frame of 1311 bp was found. The deduced 437 amino acid sequence showed a high degree of identity to the beta-succinyl-CoA synthetase of Escherichia coli (46%), the mitochondrial beta-succinyl-CoA synthetase from pig (48%) and the hydrogenosomal beta-succinyl-CoA synthetase from Trichomonas vaginalis (49%). The G + C content of the succinyl-CoA synthetase coding sequence (43.8%) was considerably higher than that of the 5' (14.8%) and 3' (13.3%) non-translated flanking sequences, as has been observed for other genes from N. frontalis. The codon usage pattern was biased, with only 34 codons used and a strong preference for a pyrimidine (T) in the third positions of the codons. The coding sequence of the beta-succinyl-CoA synthetase cDNA was cloned in an E. coli expression vector encoding a 6(His) tag. The recombinant protein was purified by affinity binding and used to produce polyclonal antibodies. The anti-succinyl-CoA synthetase serum recognized a 45 kDa protein from a N. frontalis fraction enriched for hydrogenosomes and similar polypeptides in two related anaerobic fungi, Piromyces rhizinflata (45 kDa) and Caecomyces communis (47 kDa). Immunocytochemical experiments suggest that succinyl-CoA synthetase is located in the hydrogenosomal matrix. Staining for SCS activity in native electrophoretic gels revealed a band with an apparent molecular weight of approximately 330 kDa. The C-terminus of the succinyl-CoA synthetase sequence was devoid of the typical targeting signals identified so far in microbody proteins, indicating that N. frontalis uses a different signal for sorting SCSB into hydrogenosomes. Based on comparisons with other proteins we propose a putative N-terminal targeting signal for succinyl-CoA synthetase of N. frontalis that shows some of the features of mitochondrial targeting sequences.
Brondijk
T H
TH
Laboratoire de Biologie Cellulaire Fongique, CNRS UMR 5534, Université Lyon I, Villeurbanne, France.
Durand
R
R
van der Giezen
M
M
Gottschal
J C
JC
Prins
R A
RA
Fèvre
M
M
D000595:Amino Acid Sequence; D000693:Anaerobiosis; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D003062:Codon; D018076:DNA, Complementary; D004271:DNA, Fungal; D004926:Escherichia coli; D005656:Fungal Proteins / Q000235:genetics*; D005658:Fungi / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D015388:Organelles / Q000378:metabolism; D012331:RNA, Fungal; D011994:Recombinant Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D013389:Succinate-CoA Ligases / Q000235:genetics* / Q000378:metabolism
D003062:Codon; D018076:DNA, Complementary; D004271:DNA, Fungal; D005656:Fungal Proteins; D012331:RNA, Fungal; D011994:Recombinant Proteins; D013389:Succinate-CoA Ligases; C103754:succinyl CoA hydrogenosomal beta subunit, Neocallimastix frontalis