{{tag>beta}}


======  Beta Helix =======

In this mainly beta fold, the polypeptide chain is wound into a large right-handed coil (or super helix).
There are two different types of beta helix, one with two [[glossary:beta_sheet | beta sheets]], and one with three beta
sheets. In our classification scheme we describe these as 2-solenoid and 3-solenoid beta
[[glossary:architecture | architectures]], respectively.

__2-solenoid__

This architecture comprises of two flat beta sheets
packed tightly against one another. It has a highly
distinctive and repetitive [[glossary:beta_strand | strand]] connectivity,
which distinguishes it from the two layer sandwich architecture.
The chain continually alternates between the two sheet layers whilst progressing in a
spiraling motion from one end of the structure to the other, hence the
term 'solenoid.' This could also be classified as a 2-layer beta sandwich but
its unusual lack of curvature and its unusual topology have led to it being
identified separately.

__3-solenoid__

Structures with this architecture comprise three beta sheets which
have a distinctive strand connectivity. The chain visits each sheet
in turn and is progressively wound around the principal axis in
the same direction.

===== References =====

{{pubmed>long:8081735}}
{{pubmed>long:8081738}}