Baxi M D, Vishwanatha J K
Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha 68198-4525, USA.
Biochemistry. 1995 Aug 1;34(30):9700-7. doi: 10.1021/bi00030a007.
A 37 kDa protein that binds to diadenosine tetraphosphate (Ap4A) was purified from human HeLa cells and identified as uracil DNA glycosylase/glyceraldehyde-3-phosphate dehydrogenase (UDG/GAPDH). Utilizing photoaffinity labeling with [alpha-32P]8N3-Ap4A, an Ap4A binding protein of 37 kDa was identified from HeLa cell nuclear extracts. The 37 kDa protein was purified to homogeneity and subjected to trypsin digestion followed by amino acid sequence analysis. Two peptide sequences were determined and both had complete identity with the amino acid sequence of the 37 kDa polypeptide of UDG/GAPDH. Purified UDG/GAPDH binds to Ap4A with the same affinity as the HeLa cell nuclear 37 kDa Ap4A binding protein, and monoclonal antibodies to UDG/GAPDH cross-react with the 37 kDa Ap4A binding protein. UDG/GAPDH has been previously demonstrated to have numerous nonglycolytic activities. The UDG function is involved in DNA repair by excision of uracil from DNA. GAPDH is a RNA binding protein and binds to tRNA and AU-rich RNA. The AU-rich RNA binding has been implicated in the regulation of AU-rich element dependent mRNA turnover and translation. The identification of UDG/GAPDH as an Ap4A binding protein may be physiologically relevant to the proposed role of Ap4A as a regulatory nucleotide in cell growth.
一种与二腺苷四磷酸（Ap4A）结合的37 kDa蛋白质从人HeLa细胞中纯化出来，并被鉴定为尿嘧啶DNA糖基化酶/甘油醛-3-磷酸脱氢酶（UDG/GAPDH）。利用[α-32P]8N3-Ap4A进行光亲和标记，从HeLa细胞核提取物中鉴定出一种37 kDa的Ap4A结合蛋白。将该37 kDa蛋白纯化至同质，用胰蛋白酶消化，然后进行氨基酸序列分析。确定了两个肽序列，它们与UDG/GAPDH的37 kDa多肽的氨基酸序列完全一致。纯化的UDG/GAPDH与Ap4A结合的亲和力与HeLa细胞核37 kDa Ap4A结合蛋白相同，并且针对UDG/GAPDH的单克隆抗体与37 kDa Ap4A结合蛋白发生交叉反应。此前已证明UDG/GAPDH具有多种非糖酵解活性。UDG功能通过从DNA中切除尿嘧啶参与DNA修复。GAPDH是一种RNA结合蛋白，与tRNA和富含AU的RNA结合。富含AU的RNA结合与富含AU元件依赖性mRNA周转和翻译的调节有关。将UDG/GAPDH鉴定为Ap4A结合蛋白可能在生理上与Ap4A作为细胞生长中的调节核苷酸的假定作用相关。
