Giantin or Golgin subfamily B member 1 is a protein that in humans is encoded by the GOLGB1 gene. GOLGB1, also known as Giantin and Macrogolgin, is a 360 to 400 kDa member of the Golgin protein family. GOLGB1 is an integral component of the Golgi membrane that associates with the cytoskeleton. It may be involved in both forming intercisternal cross-bridges that mediate stacking in Golgi complexes, and in reorganizing the complexes after they fragment during mitosis. GOLGB1 has also been identified as an autoantigen in chronic rheumatoid arthritis, and in the autoimmune disease Sjoegren syndrome. Human GOLGB1 is 3259 amino acids (aa) in length, and over aa 1596-1702, shares 92% and 91% sequence identity with its mouse and rat orthologs, respectively.