Lactoperoxidase-catalyzed iodination of chloroplast membranes. I. Analysis of surface-localized proteins

C. J. Arntzen, P. A. Armond, C. S. Zettinger, C. Vernotte, J. M. Briantais

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19 Scopus citations


Lactoperoxidase-catalyzed iodination of chloroplast membranes has been employed to characterize the vectorial distribution of lamellar proteins. The enzymatic reaction is highly specific for only the outermost membrane components (Phillips, D. R. and Morrison, M. (1971) Biochemistry 10, 1766-1771); we have determined the distribution of 125I label and changes in photochemical activities after iodination in an effort to identify these components. Three major conclusions are evident: 1. 1. The coupling factor for photophosphorylation is highly exposed and is selectively and rapidly inhibited by the iodination reaction. 2. 2. A loss of Photosystem I activity (NADP reduction) resulted from iodination. Partial reactions indicated the effect was on electron-transport components on the reducing side of Photosystem I. There was also a limited inhibition of methyl viologen reduction. 3. 3. Iodination of intact membranes caused a reduction in rates of Photosystem II-dependent Hill reaction activity. This inhibition could not be explained solely on the basis of iodination effects on electron-transport components involved in the oxidation of water. The implications of these data with respect to previous chloroplast-membrane models are discussed.

Original languageEnglish (US)
Pages (from-to)329-339
Number of pages11
JournalBBA - Bioenergetics
Issue number3
StatePublished - Jun 28 1974
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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