Synthesis of photopigments and electron transport components in synchronous phototrophic cultures of Rhodopseudomonas sphaeroides.

C.A Wraight,D.R Lueking,R.T Fraley,S Kaplan

doi:10.1016/s0021-9258(17)38232-7

Abstract

The kinetics of synthesis and incorporation of the photosynthetic pigments and several of the major oxidative and photosynthetic electron transport components of Rhodopseudomonas sphaeroides have been studied during synchronous and asynchronous phototrophic growth. The photosynthetic pigments and cytochromes c and b, measured spectroscopically, exhibited continuous patterns of synthesis and incorporation into the membrane particulate fraction in both synchronous and asynchronous cultures. Succinic dehydrogenase and NADH-oxidase activities, present at low levelnous growth. In a previous paper, Leuking, D.R., Fraley, R.T., and Kaplan, S. ((1978) J. Biol. Chem. 253, 451-457) have shown that total cellular phospholipid is also accumulated discontinuously during synchronous growth. A continuously incorporated membrane component is thus subject to a wide variation in the membrane protein/lipid ratio. The significance of this ratio in regulating the activity of membrane proteins is discussed and the distinction between protein incorporation and function is drawn with particular reference to the photosynthetic pigments and cytochrome components and the oxidative activities measured. It is suggested that a dependence of membrane protein activity on the membrane protein to lipid ratio in vivo is of possible significance in the control of membrane synthesis and cell division.

Highlights

From the Department of Physiology and Biophysics and the Department Illinois, Urbana, Illinois 61801 of Botany, University of DONALD R
It is suggested that a dependence of membrane protein activity on the membrane protein to lipid ratio in uiuo is of possible significance in the control of membrane synthesis and cell division
The complete photosynthetic apparatus in R. sphaeroides consists of a considerable variety of distinct components which must be assembled in some functionally significant way to create a fully active system

Summary

Introduction

The photosynthetic pigments and cytochromes c and b, measured spectroscopically, exhibited continuous patterns of synthesis and incorporation into the membrane particulate fraction in both synchronous and asynchronous cultures. A continuously incorporated membrane component is subject to a wide variation in the membrane protein/lipid ratio The significance of this ratio in regulating the activity of membrane proteins is discussed and the distinction between protein incorporation and function is drawn with particular reference to the photosynthetic pigments and cytochrome components and the oxidative activities measured. Ohki [4] has found, in synchronously dividing cultures of Escherichia coli, that synthesis of cytochrome b,, turnover of phosphatidyl glycerol, and the capacity for active transport of glycerophosphate increased discontinuously, while cell surface area and total phospholipid increased continuously, as has been shown for total protein [1, 9, 10] and RNA [9]

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Results

Conclusion