Nonstructural protein 4B (NS4B) is a

viral protein A viral protein is both a component and a product of a virus. Viral proteins are grouped according to their functions, and groups of viral proteins include structural proteins, nonstructural proteins, regulatory proteins, and accessory proteins. ...

found in the

hepatitis C virus The hepatitis C virus (HCV) is a small (55–65 nm in size), enveloped, positive-sense single-stranded RNA virus of the family ''Flaviviridae''. The hepatitis C virus is the cause of hepatitis C and some cancers such as liver cancer ( hepato ...

. It has mass of 27

kDa The dalton or unified atomic mass unit (symbols: Da or u) is a non-SI unit of mass widely used in physics and chemistry. It is defined as of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state and at re ...

and probably involved in process of

intracellular membrane The endomembrane system is composed of the different membranes (endomembranes) that are suspended in the cytoplasm within a eukaryotic cell. These membranes divide the cell into functional and structural compartments, or organelles. In eukaryot ...

structure formation to allow

virus replication Viral replication is the formation of biological viruses during the infection process in the target host cells. Viruses must first get into the cell before viral replication can occur. Through the generation of abundant copies of its genome an ...

.Ella H Sklan and Jeffrey S Glenn
Chapter 8. HCV NS4B: From Obscurity to Central Stage
in "Hepatitis C Viruses: Genomes and Molecular Biology." / Tan SL. — Norfolk: Horizon Bioscience, 2006.

References

Viral nonstructural proteins Hepatitis C virus {{virus-stub