Proline‐ and alanine‐rich N‐terminal extension of the basic bovine β‐crystallin B1 chains

Abstract
The amino acid sequence of the N-terminal region of the two basic bovine β-crystallin B1 chains has been analyzed. The results reveal that βB1b is derived in vivo from the primary gene product βB1a by removal of a short N-terminal sequence. It appears that the βB1 chains have the same domain structure as observed in other β- and γ-crystallin chains. They have, however, a very long N-terminal extension in comparison with other β-chains. This extension is mainly composed of a remarkable Pro- and Ala-rich sequence, which suggests an interaction of these structural proteins with the cytoskeleton and/or the plasma membranes of the lens cells.