Cell surface-associated proteins with molecular masses of 27 and 80 kDa found in Methylomicrobium alcaliphilum were studied. The MEALZv2_1030034 and MEALZv2_1030035 genes encoding these proteins were identified in the partially annotated genome of the methanotroph. Polypeptides MEALZv2_1030034 and MEALZv2_1030035 showed high homology (>50% identity) with the surface proteins CorA and CorB of Methylomicrobium album BG8 expressed in conditions of low copper content in the growth medium. Electron microscopic analysis with antibodies revealed localization of the 27-kDa protein in the base of the cup-shaped structures of S-layers. The mutant with an insertion in the MEALZv2_1030034 gene lost the ability to grow on the medium with methane, but grew in the presence of 0.2% methanol. In this case, the cup-shaped structures of S-layers were not bound to the cell wall but occurred as regular aggregates in the intercellular space. The 80-kDa protein was found mainly in the periplasm, had a peroxide-degrading activity, and was classified as a di-heme cytochrome c peroxidase. The mutant deficient in the MEALZv2_1030035 gene grew on methane at a high rate and had higher activities of C1 compound oxidation enzymes than did the parent strain. The role of the proteins MEALZv2_1030034 and MEALZv2_1030035 and distribution of their homologues in other methanotrophs are discussed.