Viral protein U

Retroviruses have several characteristic structural and catalytic proteins, one such auxiliary protein is a viral protein U (Vpu) which enhances virion release from human cells and also involved in the degradation of CD4, the cellular surface receptor of HIV-1.  The Vpu has no homolog in less pathogenic HIV-2 virus.  Vpu is an 81 amino acid class I membrane integral protein that is unique to human and simian immunodeficiency virus isolated from Chimpanzee and few other monkey species. The 16kDa protein Vpu protein consist of an N-terminal hydrophobic membrane anchor of 27 amino acids and a charged C-terminal hydrophilic domain of 54 amino acids that extents to the cytoplasm. The cytoplasmic domain has a conserved dual serine phosphorylation site (S52 GXXand S56 motif) that is phosphorylated by casein kinase II (1). 

Vpu is involved in viral replication an degradation of its cellular receptor CD4 and enhancement of viral particle release from macrophages and primary lymphocytes. The degradation of CD4 receptor is achieved by hijacking of protein degradation machinery of the host cells that involves ubiquitin ligases that ensures the selection of proteins to be degraded. Vpu binds to  CD4 and simultaneously recruits the βTrCP subunit of the SCF^βTrCP ubiquitin ligase complex through its constitutively phosphorylated DS₅₂GXXS₅₆ motif. In this process, Vpu was found to escape degradation, while inhibiting the degradation of βTrCP natural targets such as β-catenin and IκBα (2). Interestingly, the Vpu activity was not observed in simian cells probably due to its ability to counter act host cell restriction factor specific for human cells and may depend on Vpu binding to host channel TASK-1 protein (3). Vpu is degraded in cells arrested in early mitosis by nacodazole, the degradation process require phosphorylation of the serine 61 residue adjacent to the bTrCP-binding motif (3). Vpu has all the characteristics of signal peptide sequences (hydrophobic N-terminal and a hydrophilic C-terminal tail) when cleaved by signal peptidases stays with lipids of the signal peptidase complex, after further processing the N-0terminal region is released into cytosol where it interacts with calmodulin and preprolactin.

The Minpp1-selective antibodies were generated against synthetic peptide corresponding to residues 26-46 of the human Minpp1 (the peptide sequence is conserved in rat Minpp1). The antibodies to Minpp1are affinity purified over immobilized antigen based affinity chromatography. The purified antibodies are stabilized in antibody stabilization buffer containing preservatives. FabGennix Int. Inc., also provide western blot positive control for Minpp1 in ready-to-use buffer and limited quantities of antigenic blocking peptide is also available, please inquire about pricing and availability. FabGennix also carries many antibodies to receptor and non-receptor kinases and phosphatase, for a complete listing please visit www.FabGennix.com. FabGennix Inc. will also conjugate antibodies with fluorescent probes upon request at a reasonable cost.

For research use only, not for diagnostic or therapeutic use.