MTX3 (metaxin 3) is a mitochondrial outer membrane protein that functions as a component of the mitochondrial intermembrane bridging (MIB) complex, playing a critical role in connecting the mitochondrial outer and inner membranes at cristae junctions 1. MTX3 belongs to the metaxin protein family, which shares conserved glutathione S-transferase domains and transmembrane helices 2. While the broader metaxin family is implicated in protein transport into mitochondria, MTX3's specific mechanism involves linking the MIB-MICOS (mitochondrial contact site and cristae organization system) complex to cytoskeletal motor proteins, particularly Myo19 and its adaptor proteins Miro1/2 1. This connection is essential for maintaining proper mitochondrial cristae architecture and regulating endoplasmic reticulum-mitochondria contact sites. Notably, MTX3 deletion does not directly alter cristae structure or lipid composition, suggesting it primarily serves a bridging/organizational function rather than direct regulation of mitochondrial dynamics 1. The clinical significance of MTX3 dysfunction remains understudied; however, its role in cristae organization implies potential relevance to mitochondrial diseases and cellular bioenergetics.