세포막 단백질 중의 하나인 periplasmic 단백질이 적절한 tRNA의 존재하에 아미노산 수송기작에 관여함이 알려졌는데, 이 단백질이 alkaline phosphatase로 밝혀졌다. 이 단백질의 분자량은 gel여과 방법으로는 88,000, SDS전기 영동으로는 43,500으로 나타났는데 두 개의 동일한 단일체로 존재함을 나타내었다. 아미노산 분석과 효소 역할에 의거하여 alkaline phosphatase임이 알려졌고, 적절한 tRNA와 더불어 아미노산 수송을 크게 증가 시킴을 볼 수 있었다.
A periplasmic protein which later turned out to be alkaline phosphatase has been found to participate in amino acid transport mechanisms of Escherichia coli in the presence of appropriate tRNA. The apparent molecular weight of the purified protein was estimated to be 88,000 by gel filtration and 43,500 by SDS-polyacrylamide gel electrophoresis, indicating this protein is a dimer composed of two identical monomers. The purified protein which showed tRNA-dependent amino acid transport activity in the shocked E. coli 9723 cells has been identified as alkaline phosphatase based on its amino acid composition and enzymatic activity in addition to the molecular size. Purified alkaline phosphatase or tRNA alone did not exert any significant effect on leucine, isoleucine or valine transport, whereas simultaneous addition of these two molecules increased the amino acid transports drastically.
