Subunit distribution of the sulfhydryl groups of the F1 adenosine triphosphatase of Salmonella typhimurium

A comparison of an ATPase from the archaebacterium Halobacterium saccharovorum with the F1 moiety from the Escherichia coli ATP synthase

A purified ATPase associated with membranes from Halobacterium saccharovorum was compared with the F1 moiety from the Escherichia coli ATP synthase. The halobacterial enzyme was composed of two major (I and II) and two minor subunits (III and IV), whose molecular masses were 87 kDa, 60 kDa, 29 kDa and 20 kDa, respectively. The isoelectric points of these subunits ranged from 4.1 to 4.8, which in the case of the subunits I and II was consistent with the presence of an excess of acidic amino acids (20-22 mol/100 mol). Peptide mapping of subunits I and II denatured with sodium dodecyl sulfate showed no relationship between the primary structures of the individual halobacterial subunits or similarities to the subunits of the F1 ATPase from E. coli. Trypsin inactivation of the halobacterial ATPase was accompanied by the partial degradation of the major subunits. This observation, taken in conjunction with molecular masses of the subunits and the native enzyme, was consistent with the previously proposed stoichiometry of 2:2:1:1. These results suggest that H. saccharovorum, and possibly, halobacteria in general, possess an ATPase which is unlike the ubiquitous F0F1 ATP synthase.

Evolutionary relationship between Enterobacteriaceae: comparison of the ATP synthases (F1F0) of Escherichia coli and Klebsiella pneumoniae

The ATP synthase complex of Klebsiella pneumoniae (KF1F0) has been purified and characterized. SDS-gel electrophoresis of the purified F1F0 complexes revealed an identical subunit pattern for E. coli (EF1F0) and K. pneumoniae. Antibodies raised against EF1 complex and purified EF0 subunits recognized the corresponding polypeptides of EF1F0 and KF1F0 in immunoblot analysis. Protease digestion of the individual subunits generated an identical cleavage pattern for subunits alpha, beta, gamma, epsilon, a, and c of both enzymes. Only for subunit delta different cleavage products were obtained. The isolated subunit c of both organisms showed only a slight deviation in the amino acid composition. These data suggest that extensive homologies exist in primary and secondary structure of both ATP synthase complexes reflecting a close phylogenetic relationship between the two enterobacteric tribes.

Isolation of a fourth cysteinyl-containing peptide of the alpha-subunit of the F1 ATPase from Escherichia coli necessitates revision of the DNA sequence

The rapid determination of cysteinyl residues by Creighton's method [(1980) Nature 284, 487-489] led to the discovery of a discrepancy between protein and DNA sequence data in the alpha-subunit of the F1 ATPase from Escherichia coli [(1984) Arch. Biochem. Biophys. 229, 320-328]. We have isolated a cysteinyl-containing decapeptide from the alpha-subunit with a protein sequence (AGCAMGEYFR) which is only partially recognizable from DNA data. Re-sequencing of DNA in the region coding for the peptide has resulted in two corrections: insertion of a cytosine before position 715 and deletion of a thymine at position 731 of the uncA gene.

Thiol modification as a probe of conformational forms of the F1 ATPase of Escherichia coli and of the structural asymmetry of its beta subunits

The sulfhydryl groups of soluble and membrane-bound F1 adenosine triphosphatase of Escherichia coli were modified by reaction with the fluorescent thiol reagents 5-iodoacetamidofluorescein, 2-[(4'-iodoacetamido)anilino]naphthalene-6-sulfonic acid 4-[N-(iodoacetoxy)ethyl-N-methyl]amino-7-nitrobenzo-2-oxa-1,3-d iaz ole and 2-[(4'-maleimidyl)anilino]naphthalene-6-sulfonic acid. Whereas gamma and delta subunits were always labeled by these reagents, the beta subunit reacted preferentially in the soluble enzyme, and the alpha subunit in the membrane-bound enzyme. This suggests that the soluble enzyme undergoes a conformational change on binding to the membrane. The three beta subunits of the soluble ATPase did not react with chemical reagents in a similar manner. One beta subunit was cross-linked to the epsilon subunit on treatment of the ATPase with 1-ethyl-3-[3-(dimethyl-amino)propyl]carbodiimide, as observed previously by Lötscher et al. [Biochemistry (1984) 23, 4134-4140]. A second beta subunit, which did not cross-link to the epsilon subunit, was modified preferentially by the fluorescent thiol reagents and by 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole. The third beta subunit was less chemically reactive than the others. Both alpha and beta subunits of the soluble 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole-modified enzyme were labeled by the fluorescent thiol reagents. Thus, the modified enzyme, which is inactive, probably has a different conformation from the native soluble ATPase.