Organization of the photosynthetic membrane in maize mesophyll and bundle sheath chloroplasts studied by two-dimensional gel electrophoresis

Abstract

Polypeptide composition and the distribution of Photosystem II polypeptides were studied in mesophyll and bundle sheath chloroplasts of maize by using a modified two-dimensional gel electrophoresis technique of O'Farrell (J. Biol. Chem. (1975) 250, 4007–4021). The modifications were LiDS solubilization instead of SDS, reverse isofocusing and sensitive silver staining procedure. This high-resolution technique allowed us to separate 160 polypeptides in the two types of thylakoid membrane. We found that both types of lamella contained nearly equal amounts of polypeptides, but 73 polypeptides were different in the two preparations. In mesophyll thylakoids, 75 polypeptides out of 140 were found to be characteristic, and 54 of them were exclusively present in mesophyll preparations. In bundle sheath, 24 polypeptides out of 106 were characteristic and 19 of these polypeptides were exclusively present in bundle sheath lamellae. In functional Photosystem II prepared from maize thylakoids, 68 individual polypeptides could be distinguished. Most of these polypeptides were present in both mesophyll and bundle sheath lamellae, but 19 of them were more pronounced in mesophyll than in bundle sheath lamellae. On the other hand, 11 polypeptides of Photosystem II were distinctly different in mesophyll and bundle sheath lamellae. These differences may be in close connection with the Photosystem II heterogeneity existing in the two types of thylakoid.