<prompt> The immunoglobulin lacking hinge region isIg AIg GIg DIg E  <response>: Hinges contribute to flexibility of immunoglobulin molecules. They contain cysteine and proline. Cysteine provides interchain linkage.Proline cannot be incorporated into secondary structure of immunoglobulin molecules. The immunoglobulins Ig M Ig E lack the hinge region. They have an extra domain in the constant region-Ch4 