Formation of tyrosine O-sulfate by mitochondria and chloroplasts of Euglena

Abstract

Mitochondria that have been purified from cells of light-grown wild-type Euglena gracilis Klebs var. bacillaris Cori or dark-grown mutant W 10BSmL and incubated with 35SO 4 2− and ATP accumulate a labeled compound in the surrounding medium. This compound is also labeled when mitochondria are incubated with [ 14C]tyrosine and nonradioactive sulfate under the same conditions. This compound shows exact coelectrophoresis with synthetic tyrosine O-sulfate at pH 2.0, 5.8, and 8.0, and yields sulfate and tyrosine on acid hydrolysis. Treatment with aryl sulfatase from Aerobacter aerogenes yields sulfate and tyrosine but no tyrosine methyl ester; no hydrolysis of tyrosine methyl ester to tyrosine is observed under identical conditions, ruling out methyl esterase activity in the aryl sulfatase preparation. Thus the compound is identified as tyrosine O-sulfate. No tyrosine O-sulfate is found outside purified developing chloroplasts of Euglena incubated with 35SO 4 2− and ATP, but both chloroplasts and mitochondria accumulate labeled tyrosine- O-sulfate externally when incubated with adenosine 3′-phosphate 5′-phospho[ 35S]-sulfate (PAP 35S). Since tyrosine does not need to be added, it must be provided from endogenous sources. Labeled tyrosine O-sulfate is found in the free pools of light-grown Euglena cells grown on 35SO 4 2− or in dark-grown cells incubated with 35SO 4 2− in light, but none is found in the medium after cell growth. No labeled tyrosine O-sulfate is found in Euglena proteins (including those in extracellular mucus) after growth or incubation of cells with 35SO 4 2− or after incubation of organelles with 35SO 4 2− and ATP or PAP 35S, ruling out sulfation of the tyrosine in protein or incorporation of free-pool tyrosine O-sulfate into protein. The system forming tyrosine O-sulfate is membrane-bound and may be involved in transporting tyrosine out of the organelles.