CONTENTS:

Structure

Summary

Virion Structure

Adenoviruses are non-enveloped double stranded DNA viruses. They have an icosahedral capsid that is 70 – 100 nm in diameter. This capsid is composed of 252 capsomeres called hexons and pentons. There are a total of 240 hexons and 12 pentons. One penton is located at each of the 12 vertices of the capsid and is surrounded by 5 other capsomeres. Each penton is composed of a base and a fiber, whose length varies among serotypes. The penton base is a pentamer of polypeptide III. Extending from the pentamer base is a trimeric fiber protein composed of polypeptide IV with a knob at the end. The fiber protein has hemaggluttinin activity although the complementary receptor on the red blood cell is unknown.

Each hexon is a trimer of a single protein, polypeptide II. The 240 hexons composing the faces of the icosahedral capsid are each surrounded by six other capsomeres. This network of hexons, constructing the individual faces of the icosahedral capsid, is further stabilized by polypeptides VI, VIII and IX.

The core of the virion contains the linear double stranded DNA genome of the virus and four proteins. These proteins are polypeptides V and VII, a terminal protein (TP) and the mu protein. Polypeptide V is thought to span between the core and the capsid perhaps functioning to help position the two relative to one another. Serving a histone like function, the viral DNA wraps around polypeptide VII. This protein is basic and helps to neutralize the negative charge of the DNA. The terminal protein (TP) aids in viral replication while the function of the mu protein remains unknown.

The viral genome is linear and double stranded with inverted terminal repeats. These repeat regions enable the formation of panhandle structures, which are for replication. Within each terminal repeat, there is an origin of replication meaning each virus contains two origins. There are eight transcriptional units encoded within the genome. Five are for early events (E1A, E1B, E2, E3, and E4), two are delayed early event (IX, IVa2) and one is a late unit (L). Each unit is capable of producing multiple mRNA’s.