Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:3.4.24.27 (
thermolysin
)
1,894
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
In this report we demonstrate that a 51-kDa outer-envelope membrane protein (
P51
) is involved in protein translocation into chloroplasts. Furthermore it is shown that phosphorylation of
P51
is functionally related to the process of binding and/or importing precursor proteins into chloroplasts. Several lines of evidence have been obtained supporting this suggestion. First, protein import into chloroplasts was inhibited by the membrane-impermeable agent pyridoxal 5'-phosphate, which has been shown to react with a component of the protein-import apparatus. Phosphorylation of envelope membrane polypeptides using [gamma-32P]ATP in the presence of pyridoxal 5'-phosphate resulted in an increased incorporation of 32P radiolabel into a 51-kDa membrane polypeptide (
P51
). A close correlation between the inhibition of protein import and the increase in the phosphorylation state of
P51
, both as a function of PLP concentration, was observed. Second, binding of purified precursor proteins to chloroplasts resulted in a specific increase in the phosphorylation state of
P51
. This effect was not exerted by the mature form of the precursor protein lacking the presequence. Third, internally generated ATP was able to compete specifically with externally added [gamma-32P]ATP for the phosphorylation of
P51
. Fourth, digestion of the outer-envelope membrane with low amounts of
thermolysin
resulted in a loss of protein import activity, which was associated with the removal of the phosphorylation site of
P51
. Phosphorylation of
P51
proceeds with an apparent Km (ATP) of about 5 microM, which is much lower than the ATP concentration required for the protein translocation itself. We suggest that two different ATP-dependent processes are involved in protein translocation into chloroplasts.
P51
represent presumably a regulatory component of the protein-import apparatus or the protein receptor itself.
...
PMID:Phosphorylation of a 51-kDa envelope membrane polypeptide involved in protein translocation into chloroplasts. 340 89
