A molecular map of titin/connectin elasticity reveals two different mechanisms acting in series.
In the I-band of skeletal muscle sarcomeres, the elastic region of titin consists of immunoglobulin (Ig) domains, and non-modular regions rich in proline, hydrophobic, and charged residues (PEVK). Using immunoelectron microscopy with sequence-assigned monoclonal antibodies, we demonstrate that extension of the Ig regions in M. psoas occurs largely at sarcomere lengths between 2 and 2.8 micron, decreasing in slope towards higher lengths. The Ig domains do not unfold. Above 2.6 micron, length changes are increasingly due to the PEVK-rich regions. We therefore propose that rubber-like properties of the PEVK-rich regions are mainly contributing to skeletal titin elasticity.
Gautel
M
M
European Molecular Biology Laboratory, Biological Structures Division, Heidelberg, Germany. Gautel@EMBL-Heidelberg.DE
Goulding
D
D
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D000911:Antibodies, Monoclonal; D064211:Connectin; D004548:Elasticity; D018604:Epitope Mapping / Q000379:methods; D007136:Immunoglobulins / Q000737:chemistry; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000737:chemistry*; D017510:Protein Folding; D011494:Protein Kinases / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D016658:Psoas Muscles; D011817:Rabbits; D012518:Sarcomeres / Q000737:chemistry* / Q000648:ultrastructure
D000596:Amino Acids; D000911:Antibodies, Monoclonal; D064211:Connectin; D007136:Immunoglobulins; D009124:Muscle Proteins; D011494:Protein Kinases