A thioredoxin family protein of the apicoplast periphery identifies abundant candidate transport vesicles in Toxoplasma gondii.
Toxoplasma gondii, which causes toxoplasmic encephalitis and birth defects, contains an essential chloroplast-related organelle to which proteins are trafficked via the secretory system. This organelle, the apicoplast, is bounded by multiple membranes. In this report we identify a novel apicoplast-associated thioredoxin family protein, ATrx1, which is predominantly soluble or peripherally associated with membranes, and which localizes primarily to the outer compartments of the organelle. As such, it represents the first protein to be identified as residing in the apicoplast intermembrane spaces. ATrx1 lacks the apicoplast targeting sequences typical of luminal proteins. However, sequences near the N terminus are required for proper targeting of ATrx1, which is proteolytically processed from a larger precursor to multiple smaller forms. This protein reveals a population of vesicles, hitherto unrecognized as being highly abundant in the cell, which may serve to transport proteins to the apicoplast.
DeRocher
Amy E
AE
Seattle Biomedical Research Institute, 307 Westlake Ave. N., Seattle, WA 98109, USA.
Coppens
Isabelle
I
Karnataki
Anuradha
A
Gilbert
Luke A
LA
Rome
Michael E
ME
Feagin
Jean E
JE
Bradley
Peter J
PJ
Parsons
Marilyn
M
D000818:Animals; D005810:Multigene Family; D015388:Organelles / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013879:Thioredoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014122:Toxoplasma / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D022161:Transport Vesicles / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D015800:Protozoan Proteins; D013879:Thioredoxins