Molecular analysis of a cytoplasmic dynein light intermediate chain reveals homology to a family of ATPases

Abstract

Cytoplasmic dynein is a multi-subunit complex involved in retrograde organelle transport and some aspects of mitosis. In previous work we have cloned and sequenced cDNAs encoding the rat cytoplasmic dynein heavy and intermediate chains. Here we report the cloning of the remaining class of cytoplasmic dynein subunits, which we refer to as the light intermediate chains (LICs: 53–59 kDa). Four LIC electrophoretic bands were resolved in purified bovine cytoplasmic dynein preparations by one-dimensional gel electrophoresis. These four bands were simplified to two bands (LIC53/55 and LIC57/59) by alkaline phosphatase treatment. N-terminal amino acid sequence was obtained from a total of 11 proteolytic peptides generated from both LIC53/55 and LIC57/59. Overlapping cDNA clones encoding LIC53/55 were isolated by oligonucleotide screening using probes based on the LIC53/55 peptide sequence. The cDNA sequence contained a 497 codon open reading frame encoding a polypeptide with a molecular mass of approximately 55 kDa. Each of the LIC53/55 peptides was found within the deduced amino acid sequence, as well as four of the LIC57/59 peptides. Analysis of the LIC53/55 primary sequence revealed homology with the ABC transporter family of ATPases in the region surrounding the P-loop sequence element. Together these data identify the LICs as a novel family of dynein subunits with potential ATPase activity. They also reveal that the complexity of the LICs is due to both post-translational modification and the existence of at least two LIC polypeptides for which we propose the names LIC-1a and LIC-2.

Dynein light intermediate chains as pivotal determinants of dynein multifunctionality

“…LIC1 and LIC2 are found in cytoplasmic dynein 1, whereas LIC3 assembles into cytoplasmic dynein 2 (which is confined to the cilioplasm) (Grissom et al, 2002;Hou et al, 2004). This article will focus on LIC1 and LIC2 (henceforth referred to as LICs), which are present in mutually exclusive dynein complexes (LIC1-dynein and LIC2dynein) (Hughes et al, 1995;Tynan et al, 2000) that can perform both overlapping and unique cellular functions (Fig. 1).…”

Light Chain 1 from the Chlamydomonas Outer Dynein Arm Is a Leucine-Rich Repeat Protein Associated with the Motor Domain of the γ Heavy Chain

“…Some dyneins contain additional polypeptides that do not readily fall into the classes described above. For example, cytoplasmic dynein has four light intermediate chains that are distantly related to ABC transporters ( , ).…”

Cytoplasmic Dynein Contains a Family of Differentially Expressed Light Chains

“…The cytoplasmic dynein complex has a total mass of ∼1.25 MDa and consists of two heavy chains (HCs; 2 ∼530 kDa) that contain the motor and ATP hydrolytic sites (reviewed in ref 9), several (probably two) copies of a 74 kDa intermediate chain (IC74) (10) that is a member of the WD (G β ) repeat family (11) and therefore likely forms a β-propeller structure (12), four light intermediate chains (LICs) of 50-60 kDa that are distantly related to ABC transporters (13,14), and several light chains (LCs) with masses less than ∼22 kDa (15,16).…”

“…Intriguingly, recent studies have uncovered considerable heterogeneity in the polypeptides that go to form this motor enzyme, which may well reflect specific requirements for specialized motor, cargo-binding, and/or regulatory activities within different cell and tissue types. The observed heterogeneity derives both from different gene products for a given component (e.g., there are two IC74 genes and three classes of cytoplasmic HC known at present; 17,18) and from the multiple variants generated by differential phosphorylation and/or alternative splicing (e.g., IC74 and the LICs) (10,13,14,(19)(20)(21).…”