Photocontrol and processing of LHCP II apoprotein in Euglena: Possible role of Golgi and other cytoplasmic sites

Schiff, Jerome A.; Schwartzbach, Steven D.; Osafune, Tetsuaki; Hase, Eiji

doi:10.1016/1011-1344(91)80262-g

Cited by 31 publications

(40 citation statements)

References 26 publications

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“…When the algae are grown under a 12:12 light:dark (LD) regime, Rubisco is synthesized from about midnight to midday (LDT 18 to 6), while PCP is synthesized from dawn to dusk (LDT 0 to 12) (Markovic et al, 1996). We found that nuclear-encoded proteins passed through the Golgi on route to the plastid, as has been shown for Euglena (Schiff et al, 1991). Furthermore, we show that the dinoflagellate plastid-directed protein leader sequences are functionally similar to those found in Euglena.…”

supporting

confidence: 59%

Plastid ultrastructure defines the protein import pathway in dinoflagellates

Nassoury

Cappadocia

Morse

2003

Journal of Cell Science

103

143

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Eukaryotic cells contain a variety of different compartments that are distinguished by their own particular function and characteristic set of proteins. Protein targeting mechanisms to organelles have an additional layer of complexity in algae, where plastids may be surrounded by three or four membranes instead of two as in higher plants. The mechanism of protein import into dinoflagellates plastids, however, has not been previously described despite the importance of plastid targeting in a group of algae responsible for roughly half the ocean's net primary production. Here, we show how nuclear-encoded proteins enter the triple membrane-bound plastids of the dinoflagellate Gonyaulax. These proteins all contain an N-terminal leader sequence with two distinct hydrophobic regions flanking a region rich in hydroxylated amino acids (S/T). We demonstrate that plastid proteins transit through the Golgi in vivo, that the first hydrophobic region in the leader acts as a typical signal peptide in vitro, and that the S/T-rich region acts as a typical plastid transit sequence in transgenic plants. We also show that the second hydrophobic region acts as a stop transfer sequence so that plastid proteins in Golgi-derived vesicles are integral membrane proteins with a predominant cytoplasmic component. The dinoflagellate mechanism is thus different from that used by the phylogenetically related apicomplexans, and instead, is similar to that of the phylogenetically distant Euglena,whose plastids are also bound by three membranes. We conclude that the protein import mechanism is dictated by plastid ultrastructure rather than by the evolutionary history of the cell.

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supporting

confidence: 59%

Plastid ultrastructure defines the protein import pathway in dinoflagellates

Nassoury

Cappadocia

Morse

2003

Journal of Cell Science

103

143

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“…Euglena pLHCPII is synthesized on membrane-bound polysomes (11) and transported to the ER and Golgi appa-ratus prior to chloroplast localization (10,13). Two other Euglena cytoplasmically synthesized chloroplast proteins, PBGD (20,29) and SSU (13), are transported directly into the chloroplast.…”

Section: Resultsmentioning

confidence: 99%

“…Euglena pLHCPIIs are unique polyproteins encoded by 6.6-and 9.5-kb mRNAs (8). A Euglena pLHCPII genomic clone (GC18) encodes five mature LHCPIIs separated by decapeptide linkers (9,10). The LHCPIIs can be divided into three groups.…”

mentioning

confidence: 99%

“…Euglena pLHCPII is synthesized on membrane-bound ribosomes as found for proteins transported into the endoplasmic reticulum (ER) rather than on free ribosomes as normally found for cytoplasmically synthesized chloroplast proteins (4,11). Immunogold electron microscopy localizes Euglena LHCPII to the Golgi apparatus and chloroplast when LHCPII is being synthesized, while at times when LHCPII is not being synthesized, an immunoreaction is seen only in the chloroplast (10,13). It thus appears that Euglena pLHCPII is transported into the ER prior to chloroplast localization.…”

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confidence: 99%

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The presequence of Euglena LHCPII, a cytoplasmically synthesized chloroplast protein, contains a functional endoplasmic reticulum-targeting domain.

Kishore

Muchhal

Schwartzbach

1993

Proc. Natl. Acad. Sci. U.S.A.

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The precursor to the Euglena light-harvesting chlorophyll a/b-binding protein of photosystem II (pLHCPII) is unique; it is a polyprotein, synthesized on membrane-bound ribosomes and transported to the Golgi apparatus prior to chloroplast localization. A cDNA corresponding to the 5' end of LHCPII mRNA has been isolated and sequenced. The deduced amino acid sequence of this cDNA indicates that Euglena pLHCPII contains a 141-amino acid N-terminal extension. The N-terminal extension contains three hydrophobic domains and a potential signal peptidase cleavage site at amino acid 35. Cotranslational processing by canine microsomes removed approximately 35 amino acids from an in vitro synthesized 33-kDa pLHCPII composed of a 141-amino acid N-terminal extension and a 180-amino acid partial LH-CPU unit truncated at the beginning of the third membranespanning hydrophobic domain. Processed pLHCPII was degraded by exogenous protease, indicating that it had not been translocated to the microsomal lumen. Extraction with 0.1 M Na2CO3, pH 11.5, did not remove the processed pLHCPII from the microsomal membrane. A stop-transfer membrane anchor sequence appears to anchor the nascent protein within the membrane, preventing translocation into the lumen. Taken together, these results provide biochemical evidence for a functional cleaved signal sequence within the N-terminal extension of a Euglena cytoplasmically synthesized chloroplastlocalized protein.

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“…The Euglena pLHCPll is a polyprotein composed of eight mature LHCPlls joined covalently by a decapeptide linker (Muchhal and Schwartzbach, 1992). pLHCPll is synthesized on membrane-bound polysomes (Kishore and Schwartzbach, 1992), and immunoelectron microscopy localizes LHCPll to the Golgi apparatus before LHCPll accumulation in thylakoids Schiff et al, 1991). In vivo pulse-chase experiments have shown that pLHCPll is transported as a membrane-bound polyprotein from the ER to the Golgi apparatus and from the Golgi apparatus to the chloroplast (Sulli and Schwartzbach, 1995).…”

Section: Introductionmentioning

confidence: 99%

A soluble protein is imported into Euglena chloroplasts as a membrane-bound precursor.

Sulli

Schwartzbach

1996

Plant Cell

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The Euglena precursor to the small subunit of ribulose-1,Bbisphosphate carboxylase/oxygenase (pSSU) is a polyprotein. To determine the transport route from cytoplasm to chloroplast, Euglena was pulse labeled with 35S-sulfate and the organelles were separated on sucrose gradients. After a pulse, pSSU was found in the endoplasmic reticulum (ER) and Golgi apparatus. During a chase, ER-and Golgi-localized pSSU decreased concomitant with the appearance of SSU in chloroplasts. SSU was not found in pSSU-containing ER and Golgi fractions. Na2C03 did not remove pSSU from ER or Golgi membranes, indicating that it was an integral membrane protein. pSSU was inserted in vitro into canine microsomes, and Na2C03 did not remove pSSU from the microsomal membrane. The in vivo and in vitro experiments show that Euglena pSSU is inserted into the ER membrane and transported as an integral membrane protein to the Golgi apparatus before chloroplast import and polyprotein processing.

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Photocontrol and processing of LHCP II apoprotein in Euglena: Possible role of Golgi and other cytoplasmic sites

Cited by 31 publications

References 26 publications

Plastid ultrastructure defines the protein import pathway in dinoflagellates

Plastid ultrastructure defines the protein import pathway in dinoflagellates

The presequence of Euglena LHCPII, a cytoplasmically synthesized chloroplast protein, contains a functional endoplasmic reticulum-targeting domain.

A soluble protein is imported into Euglena chloroplasts as a membrane-bound precursor.

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