Mutations within the C-Terminus of the Subunit of the Photosynthetic F1-ATPase Activate MgATP Hydrolysis and Attenuate t
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- 作者：Feng He ; Hardeep S. Samra ; Ward C. Tucker ; David R. Mayans ; Etter Hoang ; Zippora Gromet-Elhanan ; Cindy L. Berrie ; Mark L. Richter
- 刊名：Biochemistry
- 出版年：2007
- 出版时间：March 6, 2007
- 年：2007
- 卷：46
- 期：9
- 页码：2411 - 2418
- 全文大小：420K
- 年卷期：v.46,no.9(March 6, 2007)
- ISSN：1520-4995
文摘
Two highly conserved amino acid residues near the C-terminus within the 
subunit of themitochondrial ATP synthase form a "catch" with an anionic loop on one of the three 
subunits withinthe catalytic 
hexamer of the F1 segment [Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker,J. E. (1994) Nature 370, 621-628]. Forming the catch is considered to be an essential step in cooperativenucleotide binding leading to subunit rotation. The analogous residues, Arg304 and Gln305, in thechloroplast F1 subunit were changed to leucine and alanine, respectively. Each mutant was assembledtogether with and subunits from Rhodospirillum rubrum F1 into a hybrid photosynthetic F1 that carriesout both MgATPase and CaATPase activities and ATP-dependent rotation [Tucker, W. C., Schwarcz,A., Levine, T., Du, Z., Gromet-Elhanan, Z., Richter, M. L. and Haran, G. (2004) J. Biol. Chem. 279,47415-47418]. Surprisingly, changing Arg304 to leucine resulted in a more than 2-fold increase in thekcat for MgATP hydrolysis. In contrast, changing Gln305 to alanine had little effect on the kcat but completelyabolished the well-known stimulatory effect of the oxyanion sulfite on MgATP hydrolysis. The MgATPaseactivities of combined mutants with both residues substituted were strongly inhibited, whereas the CaATPaseactivities were inhibited, but to a lesser extent. The results indicate that the C-terminus of the photosyntheticF1 subunit, like its mitochondrial counterpart, forms a catch with the and subunits that modulatesthe nucleotide binding properties of the catalytic site(s). The catch is likely to be part of an activationmechanism, overcoming inhibition by free mg2+ ions, but is not essential for cooperative nucleotideexchange.
subunit of themitochondrial ATP synthase form a "catch" with an anionic loop on one of the three subunits withinthe catalytic hexamer of the F1 segment [Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker,J. E. (1994) Nature 370, 621-628]. Forming the catch is considered to be an essential step in cooperativenucleotide binding leading to subunit rotation. The analogous residues, Arg304 and Gln305, in thechloroplast F1 subunit were changed to leucine and alanine, respectively. Each mutant was assembledtogether with and subunits from Rhodospirillum rubrum F1 into a hybrid photosynthetic F1 that carriesout both MgATPase and CaATPase activities and ATP-dependent rotation [Tucker, W. C., Schwarcz,A., Levine, T., Du, Z., Gromet-Elhanan, Z., Richter, M. L. and Haran, G. (2004) J. Biol. Chem. 279,47415-47418]. Surprisingly, changing Arg304 to leucine resulted in a more than 2-fold increase in thekcat for MgATP hydrolysis. In contrast, changing Gln305 to alanine had little effect on the kcat but completelyabolished the well-known stimulatory effect of the oxyanion sulfite on MgATP hydrolysis. The MgATPaseactivities of combined mutants with both residues substituted were strongly inhibited, whereas the CaATPaseactivities were inhibited, but to a lesser extent. The results indicate that the C-terminus of the photosyntheticF1 subunit, like its mitochondrial counterpart, forms a catch with the and subunits that modulatesthe nucleotide binding properties of the catalytic site(s). The catch is likely to be part of an activationmechanism, overcoming inhibition by free mg2+ ions, but is not essential for cooperative nucleotideexchange.