Foley M, Murray L J, Anders R F
Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia.
Mol Biochem Parasitol. 1990 Jan 1;38(1):69-75. doi: 10.1016/0166-6851(90)90206-2.
The ring-infected erythrocyte surface antigen (RESA) is a 155-kDa malarial polypeptide which is released from merozoites and becomes associated with the erythrocyte membrane at the time of invasion. Inside-out vesicles (IOVs) prepared from Plasmodium falciparum-infected erythrocytes contain RESA, presumably bound to the membrane skeleton, as it is largely insoluble in Triton X-100. When these IOVs were incubated with [gamma-32P]ATP, a 155-kDa polypeptide was labeled in IOVs from infected, but not from uninfected erythrocytes. Immunoprecipitation using specific rabbit antisera confirmed that RESA is indeed a phosphoprotein. Phosphoamino acid analysis revealed phosphoserine and a small amount of phosphothreonine, but no phosphotyrosine. Labeling of intact parasitized erythrocytes with inorganic [32P]phosphate for several hours in culture resulted in RESA in Triton-insoluble extracts being phosphorylated. Labeling of synchronized parasites showed that RESA was phosphorylated only when it became associated with the erythrocyte membrane, and although RESA was abundant in mature parasites, it was not phosphorylated. RESA, released into the culture supernatants during the growth of P. falciparum, bound to IOVs prepared from normal uninfected erythrocytes, and subsequent labeling with [gamma-32P]ATP resulted in the phosphorylation of RESA. The evidence suggests that RESA is phosphorylated by an erythrocyte membrane kinase and probably not by a parasite-encoded enzyme.
环状体感染红细胞表面抗原（RESA）是一种155千道尔顿的疟疾多肽，它从裂殖子中释放出来，并在入侵时与红细胞膜结合。从恶性疟原虫感染的红细胞制备的内向外囊泡（IOV）含有RESA，推测其与膜骨架结合，因为它在很大程度上不溶于 Triton X-100。当这些IOV与[γ-32P]ATP一起孵育时，感染红细胞来源的IOV中有一个155千道尔顿的多肽被标记，而未感染红细胞来源的IOV中则没有。使用特异性兔抗血清进行免疫沉淀证实RESA确实是一种磷蛋白。磷酸氨基酸分析显示有磷酸丝氨酸和少量的磷酸苏氨酸，但没有磷酸酪氨酸。在培养中用无机[32P]磷酸盐对完整的寄生红细胞进行数小时标记，导致Triton不溶性提取物中的RESA被磷酸化。对同步化寄生虫的标记显示，RESA只有在与红细胞膜结合时才被磷酸化，尽管RESA在成熟寄生虫中含量丰富，但它并未被磷酸化。在恶性疟原虫生长过程中释放到培养上清液中的RESA，与从正常未感染红细胞制备的IOV结合，随后用[γ-32P]ATP进行标记导致RESA磷酸化。证据表明RESA是由一种红细胞膜激酶磷酸化的，可能不是由寄生虫编码的酶磷酸化的。
