<prompt> Elasticity of hea muscle mainly depends onMyosinAcitnTitinTroponin  <response>: Titin, the largest known protein with a molecular mass near 3,000,000 Da, connects the Z lines to the M lines and provides scaffolding for the sarcomere. It contains two kinds of folded domains that provide muscle with its elasticity.Ref: Ganong;s Review of medical physiology 25th edition. Page: 101 