Protein domains are units that classify a structure of a protein. Each unit typically specifies a function or an interaction of interest. Many proteins share similar domains, yet have different overall functions [1].
Domains of ALK
In order to determine the domains of ALK, several programs may be utilized. Such programs compare sequences to common domains and/or motifs that may exist within any given protein. They are a variety of programs such as Pfam and SMART that have different algorithms to achieve this, often providing similar, but slightly different results.
Figure 1: Pfam domain analysis
Figure 2: Smart domain analysis
Biological Functions of ALK Domains
MAM
MAM domain discomposed of a Meprin, A5, and Mu components. Meprin is through to be a cell surface glycoprotein. A5 is a developmentally-regulated cell surface antigen protein. Finally, Mu is a receptor-like tyrosine protein phosphatase. All together, the MAM domain is believed to be involved in an adhesive function. Due to being extracellular, it is believed that the MAM domain contributes to ligand reception.
LDLa
LDLa stands for Low-density lipoprotein receptor domain class A. This domain is involved in lipid binding. While the role this plays within ALK is still unknown, this suggests that ALK is involved in ligand binding for this domain of ALK.
Glycine Rich
While the role of the glycine rich domain in ALK is still unknown, it is known that it is necessary for proper function. In general, glycine rich domains facilitate both the RNA-binding capacity and the protein–protein interactions.
Protein tyrosine kinase
This is the only inter cellular domain within ALK. Kinases are used for protein phosphorylation, which plays a key role in most cellular activities, is a reversible. ALK is thought to interact with a number of other proteins that are involved in both proliferation and cell survival.
What are the domains in ALK Homologs?
Discussion
ALK has several domain regions involved in signal reception and signal induction. Both of which are important for the function of ALK in cancer. By investigating various domains, it is clear that some domains are not present in some model organisms. From this, human ALK appears to share the most domain similarities to the model organism of mice.