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Abstract

This chapter discusses the contribution of cytoplasmic intermediate filaments (IFs), their subunit proteins, and their interactions with organelles and other components of the cytoskeleton. The cytoskeleton of a typical eukaryotic cell consists of three filament systems—that is, microfilaments, IFs, and microtubules—as well as a number of filament-associated proteins that cross-link these systems to each other and to cell organelles. The polymerization of IF proteins is not obligatorily dependent on either accessory (protein) cofactors or exogenous energy sources, such as ATP. The entire IF proteins share a common secondary structure consisting of three distinct domains—namely, non-α-helical head, tail domains, and rod domain. The non-α-helical head and tail domains are primarily responsible for the unique reactivities or properties of the IF proteins, while the rod domain is primarily responsible for the one property all of these diverse proteins share: the ability to polymerize into 10-nm filaments.