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Protein transport via the cpTat pathway displays cooperativity and is stimulated by transport‐incompetent substrate
Author(s) -
Alder Natahan N,
Theg Steven M
Publication year - 2003
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(03)00231-x
Subject(s) - chromosomal translocation , transport protein , biophysics , cooperativity , substrate (aquarium) , chemistry , membrane transport , thylakoid , kinetics , water transport , biochemistry , microbiology and biotechnology , biology , membrane , physics , ecology , chloroplast , quantum mechanics , water flow , environmental engineering , gene , engineering
Kinetic analyses of cpTat‐mediated protein transport across the thylakoid membrane were conducted, revealing three important characteristics of this translocation pathway. First, transport via the cpTAT system displays a non‐Michaelis–Menten, sigmoidal rate–substrate relationship with an apparent Hill coefficient of 1.80, indicative of positive homotropic cooperativity. Second, the presence of transport‐incompetent substrates was found not to competitively inhibit the translocation of transport‐competent substrates. However, the presence of low concentrations of transport‐incompetent protein enhances the transport of wild type substrate. Together, these findings suggest that interaction between Tat machinery components and both transport‐competent and transport‐incompetent protein may elicit a cooperative effect on the translocation rate.