Description:
<jats:p>To investigate the transverse bilayer organization of the chlorophyll‐proteins of the three intrinsic chlorophyll‐ protein complexes, the effects of proteolytic enzymes, and an antibody against the light‐harvesting complex were compared using right‐side‐out and inside‐out thylakoid vesicles. The vesicles were isolated by aqueous polymer phase partitioning following the fragmentation of spinach thylakoids by passage through a Yeda press. Both vesicle types were agglutinated by an antiserum specific for the light‐harvesting complex, although proteo‐ lytic degradation of the complex occurred only in right‐side‐out vesicles. In addition, there are different anti‐ genic sites for the light‐harvesting complex on the inner and outer thylakoid surfaces. Polypeptides of the chlorophyll‐<jats:italic>a</jats:italic>‐protein complex of photosystem I1 were degraded by proteases at both membrane surfaces. We conclude that both these chlorophyll‐protein complexes are membrane spanning and transversely asymmetric, but that the light‐harvesting complex polypeptides accessible at the inner thylakoid surface are more resistant to proteolytic attack. In contrast, the main chlorophyll‐containing polypeptide (<jats:italic>M</jats:italic><jats:sub>r</jats:sub>= 64500) of photosystem I complex was resistant to proteolytic attack at both the outer and inner thylakoid surfaces.</jats:p>