In an
alpha-helix, the protein chain is coiled like a loosely-coiled spring.
The available X-ray crystallographic structure of PA complex with PB1 N-terminal fragment (amino acids 1-15) shows that, when bound to PA1, the secondary structure of 115 N-terminal fragment of PB1 is an
alpha-helix [5].
In the Style/Edit Global Style menu, uncheck "
alpha-helix"; the cylinders disappear.
There are two types of arrangement for secondary structures: the
alpha-helix and beta sheets.
In one case, that of a glucocorticoid receptor protein, they found a specific spiral structure -- an
alpha-helix -- that appears to spur transcription.
Studying the configuration of how calpastatin bound to the active site of the calpain complex, "we found that there was a small
alpha-helix that fit into the active site of the calpain enzyme," Greenbaum said.
Whereas a single
alpha-helix consists of an elegant spiral of 15 to 20 amino acids, the beta sheet requires 60 to 70 amino acids.