Facilitates tyrosination of alpha-tubulin in neuronal microtubules (By similarity). Phosphorylated MAP1B may play a role in the cytoskeletal changes that accompany neurite extension. Possibly MAP1B binds to at least two tubulin subunits in the polymer, and this bridging of subunits might be involved in nucleating microtubule polymerization and in stabilizing microtubules. Acts as a positive cofactor in DAPK1-mediated autophagic vesicle formation and membrane blebbing. 3 different light chains, LC1, LC2 and LC3, can associate with MAP1A and MAP1B proteins. LC1 interacts with the amino-terminal region of MAP1B. Interacts with ANP32A and TIAM2. Interacts with the tubulin tyrosine TTL (By similarity). Interacts (via C-terminus) with GAN (via Kelch domains) (PubMed:12147674, PubMed:16227972). Interacts (via N-terminus) with DAPK1 (PubMed:18195017). Interacts with TMEM185A (PubMed:15525354). Interacts with MAP1LC3B (PubMed:24089205). Interacts with KIRREL3 (PubMed:25902260). MAP1 light chain LC1 (via C-terminus): Interacts with ELAVL4; the interaction contributes to the association of ELAVL4 with microtubules (By similarity). MAP1 light chain LC1: Interacts with ELAVL2 and ELAVL3 (By similarity). Colocalizes with DAPK1 in the microtubules and cortical actin fibers. Has a highly basic region with many copies of the sequence KKEE and KKEI/V, repeated but not at fixed intervals, which is responsible for the binding of MAP1B to microtubules. LC1 is generated from MAP1B by proteolytic processing. S-nitrosylation at Cys-2464 enhances interaction with microtubules, and may act as an effector modification for neuronal nitric oxide synthase control of growth-cone size, growth-cone collapse and axon retraction. The disease is caused by variants affecting the gene represented in this entry. Belongs to the MAP1 family.