UNSPECIFIED (1997) Role of the thylakoidal processing peptidase in chloroplast protein import. In: 11th International Conference on Proteolysis and Protein Turnover, SEP 08-11, 1996, TURKU, FINLAND.

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Abstract

The biogenesis of the photosynthetic apparatus requires the import of numerous proteins into and across the thylakoid membrane. One of the pathways is a prokaryotic-type Sec pathway in which the imported protein is synthesised with an N-terminal ''signal'' peptide, translocated across the thylakoid membrane and finally processed to the mature size by a thylakoidal processing peptidase, TPP. It is now clear that two further pathways have arisen, in which the specific cleavage of TPP is utilised to complete the targeting pathway. One of these is used for lumenal proteins that are not present in cyanobacteria, raising the possibility that both substrates and translocator have arisen since the transition of endosymbiotic cyanobacterium into semi-autonomus plastid. Substrates for this translocase have presequences that resemble typical signal peptides, but subtle differences ensure that these signals are recognised by a novel, delta pH-driven translocase and not the Sec machinery. Nevertheless, these proteins appear to be processed by the ancestral TPP activity. The third pathway is utilised for integral membrane proteins containing a single transmembrane span, such as PsbW and CF0II. These proteins are likewise synthesised with cleavable signal-type presequences, but the role of the signal appears to be to simply act as a hydrophobic section in order to facilitate insertion. Once again, the signal appears to be removed by TPP.

Item Type:	Conference Item (UNSPECIFIED)
Subjects:	R Medicine
Series Name:	BIOMEDICAL AND HEALTH RESEARCH
Journal or Publication Title:	PROTEOLYSIS IN CELL FUNCTIONS
Publisher:	I O S PRESS
ISBN:	90-5199-322-6
ISSN:	0929-6743
Editor:	HopsuHavu, VK and Jarvinen, M and Kirschke, H
Date:	1997
Volume:	13
Number of Pages:	8
Page Range:	pp. 276-283
Publication Status:	Published
Title of Event:	11th International Conference on Proteolysis and Protein Turnover
Location of Event:	TURKU, FINLAND
Date(s) of Event:	SEP 08-11, 1996
URI:	http://wrap.warwick.ac.uk/id/eprint/17648

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