Stuart W D, Woodward D O
J Bacteriol. 1975 Apr;122(1):41-6. doi: 10.1128/jb.122.1.41-46.1975.
Incubation of Neurospora crassa conidia with ribonuclease (RNase) A reduces transport of L-phenylalanine by those cells. Under similar conditions, oxidized RNase A, RNase T1, and RNase T2 do not have this effect. Incubation of conidia with active RNase covalently attached to polyacrylamide beads reduces L-phenylalanine transport. This indicates that the site of enzymatic action is at the cell surface. At the lower concentration of enzyme used in this study, incubation with RNase A reduces transport of L-phenylalanine by the general (G) amino acid permease. Increasing the enzyme concentration results in reduction of transport by the neutral aromatic (N)-specific permease. The increased transport activity that accompanies onset of conidial germination is also sensitive to incubation with RNase A. Application of the enzyme to actively transporting cells does not release amino acid transported prior to enzyme addition. Cells cultured on media supplemented with [2-14C] uridine release isotopic activity after RNase A incubation. Analogous treatments with Pronase, RNase T1, RNase T2, or deoxyribonuclease I do not release isotope activity. Pronase treatment does reduce L-phenylalanine transport. Incubation of conidia with RNase A also inhibits germination of those conidia.
用核糖核酸酶（RNase）A孵育粗糙脉孢菌分生孢子会降低这些细胞对L-苯丙氨酸的转运。在类似条件下，氧化型RNase A、RNase T1和RNase T2没有这种作用。用共价连接到聚丙烯酰胺珠上的活性RNase孵育分生孢子会降低L-苯丙氨酸的转运。这表明酶促作用位点在细胞表面。在本研究中使用的较低酶浓度下，用RNase A孵育会降低通用（G）氨基酸通透酶对L-苯丙氨酸的转运。增加酶浓度会导致中性芳香族（N）特异性通透酶的转运减少。分生孢子萌发开始时伴随的转运活性增加对用RNase A孵育也敏感。将该酶应用于活跃转运的细胞不会释放添加酶之前转运的氨基酸。在补充有[2-¹⁴C]尿苷的培养基上培养的细胞在RNase A孵育后会释放同位素活性。用链霉蛋白酶、RNase T1、RNase T2或脱氧核糖核酸酶I进行类似处理不会释放同位素活性。链霉蛋白酶处理确实会降低L-苯丙氨酸的转运。用RNase A孵育分生孢子也会抑制这些分生孢子的萌发。
