ISSN:
1420-9071
Keywords:
Mitochondrial import
;
metallopeptidases
;
processing
;
matrix-targeting sequences
;
zinc-binding motif
;
holoenzyme
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Abstract Targeting signals of mitochondrial precursors are cleaved in the matrix during or after import by the mitochondrial processing peptidase (MPP). This enzyme consists of two nonidenticalα- andβ-subunits each of molecular weight of about 50 kDa. In mammals and fungi, MPP is soluble in the matrix, whereas in plants the enzyme is part of the cytochromebc 1 complex. MPP is a metalloendopeptidase which has been classified as a member of the pitrilysin family on the basis of the HXXEHX76E zinc-binding motif present inβ-MPP. Both subunits of MPP are required for processing activity. Theα-subunit of MPP, which probably recognizes a three-dimensional motif adopted by the presequence, presents the presequence toβ-MPP, which carries the catalytic active site. MPP acts as an endoprotease on chemically synthesized peptides corresponding to mitochondrial presequences. Matrix-targeting signals and MPP cleavage signals seem to be distinct, although the two signals may overlap within a given presequence. The structural element helix-turn-helix, that cleavable presequences adopt in a membrane mimetic environment, may be required for processing but is not sufficient for proteolysis. Binding of the presequence byα-MPP tolerates a high degree of mutations of the presequence.α-MPP may present a degenerated cleavage site motif toβ-MPP in an accessible conformation for processing. The conformation of mitochondrial presequences bound to MPP remains largely unknown.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01952105
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