TAILIEUCHUNG - Báo cáo khoa học: Hu-K4 is a ubiquitously expressed type 2 transmembrane protein associated with the endoplasmic reticulum

Hu-K4 is a human protein homologous to the K4L protein of vaccinia virus. Due to the presence of two HKD motifs, Hu-K4 was assigned to the family of Phospholipase D proteins although so far no catalytic activity has been shown. The Hu-K4 mRNA is found in many human organs with highest expression levels in the central nervous system. We extended the ORF of Hu-K4 to the 5¢ direction. As a consequence the protein is 53 amino acids larger than originally predicted, now harbouring a putative transmembrane domain | iFEBS Journal Hu-K4 is a ubiquitously expressed type 2 transmembrane protein associated with the endoplasmic reticulum Antonia Munck Christopher Bohm Nicole M. Seibel Zara Hashemol Hosseini and Wolfgang Hampe Center of ExperimentalMedicine Institute of Biochemistry and Molecular Biology II University HospitalEppendorf Hamburg Germany Keywords topology subcellular localization gene structure expression pattern translational control Correspondence W. Hampe Institut fur Biochemie und Molekularbiologie II Molekulare Zellbiologie Universitatsklinikum Eppendorf Martinistr. 52 D-20246 Hamburg Germany Fax 49 40 42803 4592 Tel 49 40 42803 9967 E-mail hampe@ Received 2 December 2004 revised 1 February 2005 accepted 8 February 2005 doi Hu-K4 is a human protein homologous to the K4L protein of vaccinia virus. Due to the presence of two HKD motifs Hu-K4 was assigned to the family of Phospholipase D proteins although so far no catalytic activity has been shown. The Hu-K4 mRNA is found in many human organs with highest expression levels in the central nervous system. We extended the ORF of Hu-K4 to the 5 direction. As a consequence the protein is 53 amino acids larger than originally predicted now harbouring a putative transmembrane domain. The exon intron structure of the Hu-K4 gene reveals extensive alternative splicing in the 5 untranslated region. Due to the absence of G C-rich regions and upstream ATG codons the mRNA isoform in brain may be translated with higher efficacy leading to a high Hu-K4 protein concentration in this tissue. Using a specific antiserum produced against Hu-K4 we found that Hu-K4 is a membrane-bound protein colocalizing with protein disulfide isomerase a marker of the endoplasmic reticulum. Glycosylation of Hu-K4 as shown by treatment with peptide N-glycosidase F or tunicamycin indicates that Hu-K4 has a type 2 transmembrane topology. The Hu-K4 protein was first identified as a human homologue of the .

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