Many genes are arranged along the chromosomes in groups of related genes. These groups are called gene clusters. Examples of gene clusters are the globin gene family.

TLS Online TPP Program

#Id: 8409

#Unit 2. Cellular Organization

Troponin, a complex of three polypeptides, 

TN-T (tropomyosin-binding)

TN-I  (inhibitory)

TN-C (Ca2+-binding)

TLS Online TPP Program

#Id: 8410

#Unit 2. Cellular Organization

TN-C is the calcium-binding subunit, controls the

position of TM on the surface of an actin filament through the TN-I and TN-T subunits

TLS Online TPP Program

#Id: 8411

#Unit 2. Cellular Organization

In the absence of Ca2+, muscle is relaxed

TM blocks myosin’s interaction with F-actin

TLS Online TPP Program

#Id: 8412

#Unit 2. Cellular Organization

Binding of Ca2+ ions to TN-C

triggers movement of TM to a new position on the filament, thereby exposing the myosin-binding sites on actin.

TLS Online TPP Program

#Id: 8413

#Unit 2. Cellular Organization

Troponin C is closely related to the ubiquitous 

Ca2+-binding protein calmodulin

TLS Online TPP Program

#Id: 8414

#Unit 2. Cellular Organization

Familial hypertrophic cardiomyopathy

point mutations in cardiac β-myosin heavy chain gene mutations in other genes encoding contractile proteins including myosin light chains, cardiac troponin,

and tropomyosin.